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0:00:53 > 0:00:56- Wales is almost surrounded - by the sea.
0:00:56 > 0:00:59- I'm on the west coast of Anglesey...
0:00:59 > 0:01:02- ..and the views here - are about as good as they get.
0:01:02 > 0:01:06- There exists another landscape, - beneath the waves.
0:01:07 > 0:01:10- If anything, - it's even richer than this.
0:01:10 > 0:01:14- I'm about to embark on a journey - to discover this terrain.
0:01:14 > 0:01:19- It's a journey that begins - two miles in that direction...
0:01:19 > 0:01:20- ..under the water.
0:01:22 > 0:01:26- Under the Sea
0:01:30 > 0:01:36- On the 29th of March, 1883, - a huge storm hit the Anglesey coast.
0:01:40 > 0:01:44- A ship was sailing past Rhosneigr, - en route to Glasgow...
0:01:44 > 0:01:47- ..carrying a cargo of sugar - from Java.
0:01:50 > 0:01:54- Strong winds were blowing, - the ship hit the rocks and sank.
0:02:11 > 0:02:13- Over 125 years later...
0:02:13 > 0:02:18- ..parts of the Norman Court - remain on the seabed.
0:02:20 > 0:02:24- This is the mast, - now covered in seaweed.
0:02:25 > 0:02:29- It has survived - because it was made of iron.
0:02:34 > 0:02:37- A wooden mast would long since - have decayed in the sea.
0:02:44 > 0:02:47- These are sections - of the ship's hull...
0:02:48 > 0:02:50- ..which was shattered by the sea.
0:02:53 > 0:02:56- Wherever there's a shipwreck...
0:02:56 > 0:03:01- ..in no time at all, it becomes - covered in a carpet of creatures.
0:03:01 > 0:03:07- Often, seaweed comes first, - followed by a few shellfish.
0:03:07 > 0:03:10- When a ship has been submerged - for decades...
0:03:10 > 0:03:13- ..it's a veritable zoo, - as you can see.
0:03:17 > 0:03:22- The Norman Court lies - some five metres below the surface.
0:03:25 > 0:03:26- It attracts fish.
0:03:30 > 0:03:34- It's an island of vegetation - in the middle of the sand.
0:03:38 > 0:03:41- An oasis in the desert.
0:03:49 > 0:03:50- Fish come here to forage.
0:03:52 > 0:03:55- They scour the shipwreck for food.
0:04:01 > 0:04:03- The ship also offers sanctuary.
0:04:03 > 0:04:05- It's a place to hide...
0:04:06 > 0:04:08- ..and a place to rest.
0:04:22 > 0:04:28- Very rarely will you get so close - to two members of the shark family.
0:04:30 > 0:04:32- That's exactly what we have here.
0:04:34 > 0:04:36- They're dogfish, or cat sharks.
0:04:37 > 0:04:40- They're fairly common creatures...
0:04:40 > 0:04:44- ..but it's rare - to get this close to them.
0:04:47 > 0:04:52- A dogfish is easily recognized - as a member of the shark family.
0:04:57 > 0:05:00- Like a shark, - it moves from side to side.
0:05:01 > 0:05:03- Its body is also shaped like a shark.
0:05:03 > 0:05:07- Dogfish will let you get - fairly close to them...
0:05:07 > 0:05:13- ..but when they sense danger, - they vanish with a flick of a tail.
0:05:20 > 0:05:25- As I swim around the shipwreck, - I have to remind myself...
0:05:25 > 0:05:29- ..that I'm in a Welsh sea, - not in the Caribbean.
0:05:30 > 0:05:33- I'm swimming in waters - just off Rhosneigr.
0:05:34 > 0:05:37- Swimming alongside me - are some tiny creatures.
0:05:40 > 0:05:45- Thousands of transparent balls - with long threads hanging from them.
0:05:49 > 0:05:51- These are comb jellies.
0:05:53 > 0:05:56- They're also known - as sea gooseberries.
0:05:58 > 0:06:02- They swim around constantly - and feed on plankton.
0:06:05 > 0:06:10- They look like large jellyfish - seen on the beach...
0:06:10 > 0:06:15- ..but these are far smaller - and belong to a different species.
0:06:21 > 0:06:22- This is Holyhead.
0:06:24 > 0:06:28- The sea within the harbour walls - is still almost all the time.
0:06:31 > 0:06:34- The sea wall - creates an enclosed haven.
0:06:34 > 0:06:39- It's a different marine landscape - from the one at Rhosneigr.
0:06:42 > 0:06:45- Because the sea wall - stems the tidal flow...
0:06:46 > 0:06:52- ..sediment builds up on the bedrock - and creates a muddy landscape.
0:06:54 > 0:06:56- It may seem barren...
0:06:57 > 0:06:59- ..but some experts live here.
0:07:01 > 0:07:03- This is a sea pen.
0:07:06 > 0:07:09- It belongs to the anemone family.
0:07:10 > 0:07:13- It looks like an old writing quill - standing in the mud.
0:07:17 > 0:07:20- Sea pens are very rare in Wales.
0:07:21 > 0:07:23- This is a burrowing anemone.
0:07:25 > 0:07:30- It's another creature - that burrows into the mud...
0:07:30 > 0:07:33- ..to extract nutrients - from the water.
0:07:36 > 0:07:42- Unfortunately, rubbish has been - thrown into the harbour.
0:07:45 > 0:07:49- In time, it becomes - a part of the muddy landscape.
0:07:51 > 0:07:53- Creatures use it as hiding places.
0:07:54 > 0:07:56- It's mainly crabs which do this.
0:08:06 > 0:08:09- This is a harbour crab.
0:08:14 > 0:08:18- It can move very quickly - when it feels threatened.
0:08:20 > 0:08:25- It uses its legs like miniature oars - to propel itself through the water.
0:08:41 > 0:08:44- It would make - a brilliant rugby player!
0:08:51 > 0:08:54- This is Menai Bridge Pier - on the Menai Strait.
0:08:54 > 0:08:58- Bangor University's - School of Ocean Sciences...
0:08:58 > 0:09:02- ..moors its research vessel - Prince Madog here.
0:09:03 > 0:09:08- You don't have to go far to discover - how rich Welsh seas really are.
0:09:11 > 0:09:14- This is the pier, below the surface.
0:09:17 > 0:09:21- The iron frame looks like - an enormous underwater sculpture.
0:09:23 > 0:09:26- It's covered in plumose anemones.
0:09:29 > 0:09:33- These creatures like a solid surface - on which they can grip.
0:09:34 > 0:09:37- The iron framework - fits the bill perfectly.
0:09:40 > 0:09:44- They feed by filtering tiny pieces - of plankton from the sea.
0:09:47 > 0:09:51- The tentacles help guide food - to the animal's central mouth.
0:09:54 > 0:09:58- The nutrient-rich waters - attract an array of marine life.
0:10:02 > 0:10:08- The water in the Menai Strait - flows just like a normal river.
0:10:10 > 0:10:14- For around 4,000 years - following the last Ice Age...
0:10:14 > 0:10:16- ..the Menai Strait didn't exist.
0:10:17 > 0:10:20- At that time, sea levels were low.
0:10:20 > 0:10:25- This was then a valley, with a small - river flowing from the high ground.
0:10:28 > 0:10:32- Under the Menai Suspension Bridge, - the current today is very complex.
0:10:34 > 0:10:37- The water moves - in several directions.
0:10:37 > 0:10:40- It has a real impact - on what lives below the surface.
0:10:43 > 0:10:48- The Menai Strait is among the - richest habitats in Welsh waters.
0:10:50 > 0:10:53- There's a simple reason for that.
0:10:54 > 0:10:59- An incredibly strong tide - flows in and out four times a day.
0:10:59 > 0:11:04- It carries with it - all manner of food and nutrients.
0:11:08 > 0:11:12- All the creatures seen here - filter food from the water.
0:11:14 > 0:11:16- It's a kaleidoscope of colour.
0:11:17 > 0:11:23- There are sponges, anemones, crabs - and all sorts of creatures here.
0:11:25 > 0:11:28- It's like being in an aquarium.
0:11:32 > 0:11:34- The tidal flow may be strong...
0:11:34 > 0:11:38- ..but huge storms - don't affect this habitat.
0:11:41 > 0:11:44- It's in a sheltered spot, - far from the open coast.
0:11:46 > 0:11:50- This suits the sponges - and other creatures which live here.
0:11:52 > 0:11:53- Life thrives here.
0:11:57 > 0:11:59- This is an edible crab, - the type of crab we eat.
0:12:02 > 0:12:04- It navigates the rocks expertly.
0:12:07 > 0:12:10- The velvet swimming crab - is also very mobile.
0:12:12 > 0:12:14- This is the fiercest of our crabs.
0:12:16 > 0:12:19- It takes very little - to anger this crab...
0:12:19 > 0:12:22- ..and it knows exactly - how to protect itself.
0:12:25 > 0:12:27- Here, we have two shore crabs.
0:12:27 > 0:12:29- One is stung by an anemone.
0:12:32 > 0:12:35- These are the crabs - seen on our beaches.
0:12:35 > 0:12:37- They can also be fierce.
0:12:42 > 0:12:45- Every living creature - eats something.
0:12:45 > 0:12:49- The life cycle of this sea gooseberry - is about to end.
0:12:56 > 0:13:00- Like crabs, - prawns often hide in crevices.
0:13:02 > 0:13:05- This particular crevice - is occupied.
0:13:07 > 0:13:10- It's better to share - with a friendlier relative.
0:13:16 > 0:13:20- Penmon lighthouse and Puffin Island, - to the east of Anglesey.
0:13:23 > 0:13:25- Puffin Island is made of limestone.
0:13:27 > 0:13:31- Below the surface, - the sea has eroded the limestone...
0:13:32 > 0:13:35- ..to create platforms - of white rock.
0:13:35 > 0:13:37- Seals enjoy being here.
0:13:45 > 0:13:47- These are grey seals.
0:13:49 > 0:13:51- They're playful creatures.
0:14:04 > 0:14:07- It's an honour to be in the water - with these animals.
0:14:08 > 0:14:11- They are masters of their habitat.
0:14:12 > 0:14:17- One tiny flick of their tails - and they've gone.
0:14:21 > 0:14:25- On land, they instantly - move away from people.
0:14:27 > 0:14:31- When they're underwater, - they're fearless.
0:14:37 > 0:14:39- They're inquisitive animals.
0:14:41 > 0:14:44- This pup is only about a year old.
0:14:44 > 0:14:46- He seems fascinated by my feet!
0:14:52 > 0:14:55- He seems unsure - what kind of creature I am...
0:14:55 > 0:14:59- ..but he's not afraid - to inspect me up close.
0:15:11 > 0:15:17- Down here, the seals make me look - like a clumsy bag of lard!
0:15:17 > 0:15:19- This is their habitat...
0:15:20 > 0:15:23- ..and I feel as if - they're playing tricks on me!
0:15:24 > 0:15:29- They go and hide, then come back - to see what's going on.
0:15:29 > 0:15:31- One of them even gave me a kiss!
0:15:31 > 0:15:35- He's a real sweetheart. - There he is, back again!
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0:16:37 > 0:16:40- Dinas Dinlle - on Gwynedd's north coast.
0:16:43 > 0:16:47- On the hill above the beach, - there's an old Iron Age fort.
0:16:47 > 0:16:50- Parts of the fort - have fallen into the sea.
0:16:54 > 0:16:57- The Welsh coast - is constantly eroding.
0:16:58 > 0:17:01- Part of the landscape - has been lost to the sea.
0:17:03 > 0:17:07- Underwater, near Dinas Dinlle, - is Caer Arianrhod.
0:17:08 > 0:17:14- It's a cluster of rocks which is - sometimes visible at low tide.
0:17:17 > 0:17:20- This location is named - in the Mabinogion...
0:17:20 > 0:17:24- ..in the tale about Arianrhod, - Gwydion's sister.
0:17:25 > 0:17:31- Was there really a fort here once? - Or is it merely a mythical location?
0:17:34 > 0:17:37- These rocks were deposited here - by Ice Age glaciers.
0:17:40 > 0:17:44- The sea is very shallow here - and the sun warms the water.
0:17:47 > 0:17:49- It's perfect for plants.
0:17:53 > 0:17:56- Like land plants, - marine plants are seasonal.
0:17:56 > 0:18:00- They're at their best - during spring and summer.
0:18:03 > 0:18:05- This is sea lace.
0:18:07 > 0:18:10- It's a long, thin seaweed - stretching towards the surface.
0:18:18 > 0:18:22- The rocks of Caer Arianrhod - are covered in vegetation.
0:18:24 > 0:18:26- Fish hide among the seaweed.
0:18:32 > 0:18:35- This is a corkwing wrasse.
0:18:45 > 0:18:48- This is an example - of the seaweed down here.
0:18:48 > 0:18:50- In this square metre alone...
0:18:50 > 0:18:55- ..I can see at least half a dozen - different varieties of seaweed.
0:18:57 > 0:19:02- You know you're in shallow water - when you see this green seaweed.
0:19:02 > 0:19:04- It's called sea lettuce.
0:19:11 > 0:19:13- This is the sea's pasture.
0:19:13 > 0:19:19- The combination of light, warmth - and a sheltered location...
0:19:20 > 0:19:24- ..creates a stable, - unchanging habitat.
0:19:28 > 0:19:30- It's a very rich habitat.
0:19:30 > 0:19:34- The movement of the seaweed - is at its best when the tide turns.
0:19:45 > 0:19:48- Aberdaron Bay - on the Lleyn Peninsula.
0:19:48 > 0:19:53- Like most of Wales's bays, - it's a fairly sheltered location.
0:19:53 > 0:19:57- Due to this, sand and gravel - accumulates in the bay.
0:19:59 > 0:20:04- But in one part, an unnatural reef - has been created by a shipwreck.
0:20:09 > 0:20:11- Seaweed conceals the ship...
0:20:12 > 0:20:14- ..but the bow is visible.
0:20:18 > 0:20:23- The ship sank over a century ago - after hitting a rock in the bay.
0:20:26 > 0:20:31- It may be an iron ship, but the sea - is still breaking it up gradually.
0:20:36 > 0:20:39- Very little of the hull remains...
0:20:40 > 0:20:42- ..but the boiler is prominent.
0:20:45 > 0:20:47- The wreck has attracted fish.
0:20:49 > 0:20:52- Several species can be seen here.
0:20:53 > 0:20:57- This is a shoal - of two-spotted gobies.
0:21:04 > 0:21:07- A pouting hides beneath the ship.
0:21:15 > 0:21:19- The larger fish without the stripes - is a poor cod.
0:21:24 > 0:21:27- These fish are common - on the Welsh coast.
0:21:29 > 0:21:31- This fish is anything but common.
0:21:31 > 0:21:35- This trigger fish - was near the wreck.
0:21:38 > 0:21:42- It's quite scarce - and it's rarely seen this far north.
0:21:44 > 0:21:47- It likes to hide between the rocks.
0:21:47 > 0:21:50- Its shape helps it do just that.
0:21:59 > 0:22:03- Further out in Aberdaron Bay - are the Gwylan Islands.
0:22:04 > 0:22:07- They are made of hard, ancient rock.
0:22:08 > 0:22:12- That's why they survived - in the middle of a bay.
0:22:14 > 0:22:18- The softer land surrounding them - has been lost to the sea.
0:22:23 > 0:22:27- The tidal flow around the islands - is very strong.
0:22:31 > 0:22:35- The tide usually tears through - a place like this.
0:22:38 > 0:22:42- That usually encourages a variety - of sponges to grow on the rocks.
0:22:45 > 0:22:49- This is called a carrot sponge, - for obvious reasons.
0:22:55 > 0:22:59- Sponges remain in one place, - filtering nutrients from water...
0:23:00 > 0:23:03- ..so they need - constantly flowing water.
0:23:05 > 0:23:07- That's why they thrive here.
0:23:12 > 0:23:16- I've seen sponges - in other parts of Wales...
0:23:17 > 0:23:19- ..but they were always small.
0:23:19 > 0:23:23- Look at this big yellow sponge.
0:23:23 > 0:23:26- It's as though someone - put cement on the stone.
0:23:28 > 0:23:30- It's a colourful sponge.
0:23:33 > 0:23:36- There's a scorpion spider crab - next to it.
0:23:37 > 0:23:40- It covers itself with sponges.
0:23:40 > 0:23:44- It breaks off fragments of sponge - and sticks them to its body...
0:23:45 > 0:23:46- ..as a form of camouflage.
0:23:50 > 0:23:52- A fish hides on the seabed.
0:23:56 > 0:24:00- The short-spined sea scorpion - looks just like a rock.
0:24:05 > 0:24:09- It waits for any creature - that hasn't noticed it...
0:24:09 > 0:24:12- ..and as it passes by, - catches it.
0:24:23 > 0:24:27- This is Cardigan Bay, - between Pwllheli and Abersoch.
0:24:27 > 0:24:30- It's an area of flat beaches...
0:24:30 > 0:24:34- ..where the sea has deposited - a mixture of mud, sand and gravel.
0:24:39 > 0:24:42- The flow of the sea - is always strong here.
0:24:49 > 0:24:55- There are more examples of fish - that use camouflage here.
0:24:56 > 0:25:00- The dragonet - tends to bury itself on the seabed.
0:25:02 > 0:25:06It can alter its coloration from location to location...
0:25:07 > 0:25:09- ..to match the background.
0:25:16 > 0:25:21- The tub gurnard is another creature - that lives on the seabed.
0:25:21 > 0:25:26- Its front fins have evolved - to form small fingers...
0:25:26 > 0:25:29- ..which it uses - to walk along the seabed.
0:25:35 > 0:25:39- When it swims, its fins - look just like a butterfly's wings.
0:25:45 > 0:25:48- Starfish also live on the seabed.
0:25:50 > 0:25:52- This is a spiny starfish.
0:25:54 > 0:25:58- It likes a stony beach and moves - very slowly along the seabed...
0:25:59 > 0:26:02- ..eating small creatures, - be they dead or alive.
0:26:12 > 0:26:13- .
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0:26:16 > 0:26:18- 888
0:26:22 > 0:26:24- Saint Patrick's Causeway.
0:26:24 > 0:26:31- A shingle reef which stretches - for 12 miles west...
0:26:31 > 0:26:34- ..off the coast of Ardudwy - in north Wales.
0:26:36 > 0:26:40- This causeway is in fact - made of glacial deposits...
0:26:40 > 0:26:43- ..left here - at the end of the Ice Age.
0:26:45 > 0:26:49- Saint Patrick's Causeway - is rarely visible above the sea.
0:26:51 > 0:26:54- It happens at low tide - about four times a year...
0:26:55 > 0:26:58- ..and even then, only for - about two hours at a time.
0:26:59 > 0:27:01- This is a remarkable sight.
0:27:03 > 0:27:07- You usually only see the outline - of the reef in the water.
0:27:07 > 0:27:11- There are other causeways - on the Welsh coast.
0:27:12 > 0:27:15- Sarn Cynfelyn - is north of Aberystwyth.
0:27:15 > 0:27:20- The causeway isn't as visible, - due to the shadows cast by clouds...
0:27:20 > 0:27:24- ..but the masses of rocks, - known as moraines...
0:27:24 > 0:27:27- ..can be seen stretching in a line - from the coast.
0:27:32 > 0:27:37- Below the surface, the moraine rocks - have been washed clean by the sea.
0:27:38 > 0:27:42- Among the small stones are big rocks.
0:27:53 > 0:27:58- We're familiar with the effects - of the Ice Age on the mainland...
0:27:58 > 0:28:01- ..especially in famous places - like Cwm Idwal.
0:28:01 > 0:28:05- The undersea landscape - also bears witness to the Ice Age.
0:28:05 > 0:28:09- The causeway itself - was deposited by glaciers...
0:28:09 > 0:28:13- ..but a few huge rocks - were also left behind.
0:28:13 > 0:28:17- This all happened - when the glacier melted.
0:28:17 > 0:28:21- Unlike on land, - where rocks are perhaps bare...
0:28:21 > 0:28:26- ..these are covered in vegetation - and all sorts of creatures.
0:28:29 > 0:28:32- Shallow water covers the causeways.
0:28:32 > 0:28:37- In essence, it's a reef on which - several types of seaweed grows.
0:28:38 > 0:28:41- Most of the seaweed - grows in the spring...
0:28:42 > 0:28:44- ..and dies in late summer.
0:28:46 > 0:28:50- Creatures hide among the seaweed.
0:29:05 > 0:29:08- This is a spider crab.
0:29:09 > 0:29:13- There were no spider crabs - in our waters 50 years ago...
0:29:15 > 0:29:17- ..but they're now quite common.
0:29:18 > 0:29:22- This is the largest crab - you'll find off the Welsh coast.
0:29:22 > 0:29:24- Look at that!
0:29:24 > 0:29:25- It's massive!
0:29:25 > 0:29:30- For some unknown reason, - spider crabs disappear in winter.
0:29:32 > 0:29:35- Perhaps they head to deep waters, - but no-one really knows.
0:29:36 > 0:29:38- I'd better put him back!
0:29:42 > 0:29:46- One of the reasons - why crabs move to deeper waters...
0:29:46 > 0:29:50- ..may be because this vegetation - vanishes in the winter.
0:29:51 > 0:29:56- They're certainly here - in large numbers during the summer.
0:29:59 > 0:30:03- Further down the Ceredigion coast - is New Quay.
0:30:04 > 0:30:08- It's a harbour town - with a fishing tradition.
0:30:10 > 0:30:15- At the far end of the harbour, - there's a fish processing plant.
0:30:15 > 0:30:19- Its presence has an impact - on the marine wildlife.
0:30:26 > 0:30:27- This is amazing!
0:30:29 > 0:30:31- These are dahlia anemones.
0:30:31 > 0:30:36- They're quite common - along the west coast of Wales...
0:30:38 > 0:30:42- ..but you rarely see - such a cluster of them.
0:30:43 > 0:30:49- They're here purely because - of the fish processing plant.
0:30:50 > 0:30:54- The waste thrown into the sea - by the fish processors...
0:30:54 > 0:30:57- ..feeds these anemones.
0:30:58 > 0:31:01- That waste floats in the water - all around this area.
0:31:05 > 0:31:08- This doesn't damage - the natural habitat...
0:31:08 > 0:31:10- ..but it's a good example...
0:31:11 > 0:31:15- ..of the way wildlife capitalizes - on any nourishment it can find.
0:31:18 > 0:31:24- A wide variety of fish shoal - near the harbour rocks in New Quay.
0:31:28 > 0:31:30- These are whitebait.
0:31:31 > 0:31:34- These are the small fish - that seabirds eat.
0:31:36 > 0:31:38- It's good to see - so many fish here.
0:31:38 > 0:31:42- The wealth of the sea - impacts on the wealth of the land.
0:31:44 > 0:31:48- Without these fish, - birds like puffins would vanish.
0:31:52 > 0:31:54- These are sea bass.
0:31:55 > 0:31:57- They're much bigger fish.
0:31:58 > 0:32:01- They like to shoal close to rocks - in foamy seawater.
0:32:04 > 0:32:08- These fish are very popular - on dinner tables nowadays.
0:32:14 > 0:32:18- There are caves and deep crevices - among the rocks.
0:32:21 > 0:32:23- The water is calmer here.
0:32:31 > 0:32:35- Being in a cave like this - which is full of clear water...
0:32:35 > 0:32:38- ..is like being in a huge aquarium.
0:32:40 > 0:32:43- It gives you a real sense - of the power of the waves.
0:32:44 > 0:32:47- There are some small fish here...
0:32:47 > 0:32:50- ..hiding among the seaweed - and the rocks.
0:32:52 > 0:32:53- This is a haven for them.
0:32:54 > 0:32:58- They come here to get away - from the bigger fish during the day.
0:33:02 > 0:33:06- These little fish are very rare - on the Welsh coast.
0:33:07 > 0:33:09- Transparent gobies.
0:33:13 > 0:33:16- They swim by darting here and there.
0:33:18 > 0:33:23- I've never seen such a large group - of them before.
0:33:23 > 0:33:28- So, is our marine wildlife altering - as a result of climate change?
0:33:29 > 0:33:32- At this moment in time, - nobody really knows.
0:33:36 > 0:33:40- The rocks off New Quay - are covered in mussels.
0:33:43 > 0:33:44- Crabs eat them.
0:33:46 > 0:33:49- It's like swimming - in a huge aquarium.
0:33:57 > 0:34:01- This demonstrates just how rich - in wildlife this area really is.
0:34:02 > 0:34:04- I'm surrounded by animals.
0:34:05 > 0:34:11- There's an edible crab up there - and a big lobster here.
0:34:13 > 0:34:16- I must admit, - I eat all these creatures...
0:34:16 > 0:34:21- ..but it's much better to see them - in their natural habitat.
0:34:31 > 0:34:35- Abercastle Bay on the north coast - of Pembrokeshire.
0:34:37 > 0:34:41- This part of the coast - is pounded by huge waves.
0:34:46 > 0:34:51- Beneath the waves, there's a seaweed - that can withstand the sea's power.
0:34:54 > 0:34:56- Kelp.
0:35:00 > 0:35:06- Swimming through kelp is like - flying through a rainforest canopy.
0:35:11 > 0:35:14- This sight isn't unique - to Abercastle.
0:35:14 > 0:35:20- Kelp grows along the Welsh coast - in areas where currents are strong.
0:35:20 > 0:35:24- It also grows - on the lowest parts of the beach.
0:35:25 > 0:35:28- There are several types of kelp.
0:35:28 > 0:35:31- Each has wide leaves - and strong roots.
0:35:36 > 0:35:42- You can see how this particular - variety of seaweed can withstand...
0:35:42 > 0:35:47- ..the enormous power of the waves - which sometimes pound the rocks.
0:35:48 > 0:35:51- These long leaves are like leather.
0:35:52 > 0:35:54- They're really tough.
0:35:54 > 0:35:56- The roots grip the bottom.
0:35:57 > 0:36:02- They have a stranglehold - on this old chain on the seabed.
0:36:02 > 0:36:07- It takes a lot of strength - to tear them away from it.
0:36:10 > 0:36:15- Moving through the growth - is an almost unearthly experience.
0:36:15 > 0:36:20- The shapes and the movement - look like an undersea monster.
0:36:29 > 0:36:31- This is a ballan wrasse.
0:36:31 > 0:36:35- Its Latin name is Labrus bergylta.
0:36:36 > 0:36:41- Seaweed-filled water - is this fish's favourite habitat.
0:36:48 > 0:36:53- Spider crabs have flourished here - during the past ten years.
0:36:54 > 0:36:59- They thrive in almost every habitat - the Welsh coast has to offer.
0:36:59 > 0:37:02- The spider crab - also lives in Abercastle.
0:37:09 > 0:37:10- .
0:37:13 > 0:37:13- 888
0:37:13 > 0:37:15- 888- - 888
0:37:18 > 0:37:22- Skomer Island, - west of Pembrokeshire.
0:37:22 > 0:37:27- The area around the island and parts - of the Pembrokeshire coast...
0:37:27 > 0:37:31- ..form Wales's only - Marine Nature Reserve.
0:37:33 > 0:37:38- It was so designated because - the underwater habitat is so rich.
0:37:45 > 0:37:47- There's a wide variety of life here.
0:38:04 > 0:38:08- There are more - dense kelp forests here.
0:38:11 > 0:38:15- The kelp grips the rocks - with its thick roots.
0:38:23 > 0:38:25- Just like a rainforest...
0:38:26 > 0:38:31- ..other plants grow in the shelter - offered by the underwater trees.
0:38:31 > 0:38:35- Sponges and other creatures - thrive in the undergrowth.
0:38:41 > 0:38:46- The gushing sea carries food - to feed small creatures...
0:38:46 > 0:38:49- ..which filter nourishment - from the water.
0:38:50 > 0:38:52- These are hydroids.
0:38:52 > 0:38:57- A community of tiny creatures - that live together on a frame.
0:38:57 > 0:39:01- They've built something similar - to a bush here.
0:39:04 > 0:39:09- This is the star of Skomer Island - - the sea fan.
0:39:20 > 0:39:22- Look at the size of this sea fan!
0:39:24 > 0:39:26- It must be half a metre wide.
0:39:28 > 0:39:32- A sea fan is a colony - of thousands of tiny creatures...
0:39:32 > 0:39:34- ..that all live together.
0:39:34 > 0:39:37- They filter nourishment - from the sea.
0:39:39 > 0:39:42- I never imagined - I'd see something like this here.
0:39:43 > 0:39:45- I'd only expect to see a sea fan...
0:39:46 > 0:39:49- ..in Australia, the Red Sea - or the Caribbean.
0:39:49 > 0:39:51- Anywhere but the waters of Wales!
0:39:52 > 0:39:56- I found one, and a huge one at that, - near Skomer Island.
0:39:59 > 0:40:01- This has been growing here - for a century.
0:40:04 > 0:40:08- This is the most northerly point - in Wales where you'll see a sea fan.
0:40:09 > 0:40:12- The sea is just as warm - in parts of north Wales...
0:40:13 > 0:40:18- ..but, for some reason, the sea fan - hasn't crossed Cardigan Bay yet.
0:40:24 > 0:40:25- The south Gower coast.
0:40:26 > 0:40:31- Here are two coastal areas - that are close geographically...
0:40:31 > 0:40:35- ..but which have vastly different - underwater landscapes.
0:40:35 > 0:40:40- That's due to the difference - in the sea's power in both locations.
0:40:42 > 0:40:44- This is Port-Eynon.
0:40:50 > 0:40:55- Under the sea, there's a rocky bed - and limestone reefs.
0:40:58 > 0:41:02- It's close to the shore, - but no large plants can grow here.
0:41:03 > 0:41:07- Every plant and creature is small - and stuck to the rock.
0:41:09 > 0:41:14- Anything large is smashed to pieces - by powerful waves...
0:41:14 > 0:41:17- ..but small creatures - can survive and thrive here.
0:41:20 > 0:41:23- This is a long-spined sea scorpion.
0:41:23 > 0:41:28- It's similar to its relative, - the short-spined sea scorpion...
0:41:28 > 0:41:30- ..but is slightly bigger.
0:41:30 > 0:41:33- It likes to live on the seabed.
0:41:36 > 0:41:38- It can sometimes be seen - in rock pools.
0:41:40 > 0:41:43- If you try to catch one, be careful.
0:41:43 > 0:41:47- It's spiny, and that's how - it defends itself.
0:41:47 > 0:41:51- When another creature swallows one, - they tend to spit it out...
0:41:52 > 0:41:54- ..because of the spines.
0:41:58 > 0:42:01- It has the perfect camouflage.
0:42:01 > 0:42:06- It hides on rocks, ready to pounce - on any crab or small fish.
0:42:20 > 0:42:23- Oxwich Bay is close to Port-Eynon.
0:42:25 > 0:42:29- It's a very sheltered bay - with a long, stable beach.
0:42:31 > 0:42:36- During WW2, a stricken ship - was towed to the calm waters here.
0:42:41 > 0:42:47- 60 years may have passed, - but most of it is still intact.
0:42:52 > 0:42:56- The ship was carrying goods - from New York to Glasgow.
0:42:58 > 0:43:03- It was torpedoed by a submarine - in the Irish Sea.
0:43:07 > 0:43:12- It was towed here to see - whether it was possible to save it.
0:43:14 > 0:43:15- It wasn't.
0:43:19 > 0:43:22- I'm looking through - what was once a porthole.
0:43:24 > 0:43:27- This ship has been here since 1945.
0:43:29 > 0:43:31- It's covered in vegetation.
0:43:31 > 0:43:36- Around the porthole - are dead man's fingers.
0:43:36 > 0:43:42- It's not one creature, but a cluster - of animals that live together.
0:43:42 > 0:43:46- They're really pretty, - but very aptly named.
0:43:47 > 0:43:51- They look like a dead hand - hanging in the water.
0:43:55 > 0:44:00- The wreck is still here because - the force of the waves is weak.
0:44:06 > 0:44:10- In any other location, - the sea would have shattered it.
0:44:17 > 0:44:19- Milford Haven.
0:44:19 > 0:44:22- This is actually a flooded valley.
0:44:24 > 0:44:28- At the end of the Ice Age, - only a small river flowed here.
0:44:29 > 0:44:32- Between 6,000 and 8,000 years ago...
0:44:32 > 0:44:37- ..the sea rose, flooding the valley - and creating a deep estuary.
0:44:39 > 0:44:43- That's why it's one of Britain's - most important ports today.
0:44:47 > 0:44:50- There are shipwrecks here too.
0:44:54 > 0:44:58- These are remnants of ships - sunk during World War II.
0:45:01 > 0:45:06- There are also boats - that capsized and were submerged.
0:45:08 > 0:45:10- Here they shall remain.
0:45:13 > 0:45:19- The sea around Milford Haven - isn't strong enough to destroy them.
0:45:21 > 0:45:23- They become a part of the seabed.
0:45:23 > 0:45:25- Animals and plants live on them.
0:45:31 > 0:45:32- Sea squirts...
0:45:33 > 0:45:34- ..sponges...
0:45:36 > 0:45:37- ..and anemones.
0:45:58 > 0:46:00- This sea squirt has a great name.
0:46:01 > 0:46:04- Light bulb sea squirts.
0:46:04 > 0:46:07- They look like - a collection of bulbs.
0:46:11 > 0:46:16- They all thrive because the sea's - constant movement...
0:46:16 > 0:46:18- ..carries food for them.
0:46:21 > 0:46:25- That means Milford Haven is a great - place for exotic creatures too.
0:46:29 > 0:46:32- The problem in this estuary...
0:46:33 > 0:46:37- ..is that large ships come here - from all over the world...
0:46:38 > 0:46:41- ..carrying exotic creatures - with them.
0:46:43 > 0:46:45- When they clean out the tanks...
0:46:46 > 0:46:49- ..those creatures - are released into the water.
0:46:50 > 0:46:53- Some of them then thrive - and take over...
0:46:55 > 0:47:00- ..just like the rhododendron - in Snowdonia.
0:47:01 > 0:47:05- The leathery sea squirt - seems unremarkable.
0:47:05 > 0:47:09- It's just a brown creature - living among the other creatures.
0:47:11 > 0:47:16- But it's an example of the way - our actions impact on marine life.
0:47:17 > 0:47:22- It's easy to forget about it, as you - rarely see a leathery sea squirt.
0:47:24 > 0:47:28- It's important to remember that, - unlike the land...
0:47:28 > 0:47:33- ..most of the marine landscape - is a relatively natural landscape.
0:47:36 > 0:47:39- It remains largely unaffected - by human actions.
0:47:41 > 0:47:45- That's what makes it - one of our most important landscapes.
0:47:58 > 0:48:02- On my journey - through Wales's marine landscape...
0:48:02 > 0:48:04- ..I've seen a wealth of wildlife.
0:48:13 > 0:48:16- Some people travel abroad - to see similar sights...
0:48:17 > 0:48:23- ..without realizing there are great - marine landscapes and wildlife...
0:48:23 > 0:48:25- ..much closer to home.
0:48:34 > 0:48:38- These magnificent sights - can all be seen in Wales.
0:49:08 > 0:49:10- S4C subtitles by Eirlys A Jones
0:49:10 > 0:49:11- .