0:50:50 > 0:50:57.
0:51:38 > 0:51:41Loch Creran is a conservation area,
0:51:41 > 0:51:43because of its incredible marine life.
0:51:43 > 0:51:45but what makes it so special
0:51:45 > 0:51:49are some very shy tube worms that are busy building their own city
0:51:49 > 0:51:52out there under the water and this I've got to see.
0:51:54 > 0:52:01These waters conceal some curious little worms that build tube-shaped shells around themselves.
0:52:01 > 0:52:06Those tube worms have created their own version of a tropical coral reef,
0:52:06 > 0:52:09the largest of its kind in the northern hemisphere.
0:52:13 > 0:52:16It's down there somewhere and I've got to find it.
0:52:18 > 0:52:21- Hi there.- Hi, how you doing?
0:52:21 > 0:52:25My guides in Loch Creran are David Hughes, a marine biologist
0:52:25 > 0:52:28and Emily Venables, an oceanographer.
0:52:31 > 0:52:38This loch's global claim to fame is down to the shells that the worms build around themselves.
0:52:38 > 0:52:44Each individual worm secretes a hard calcified tube around itself that it uses to protect itself.
0:52:44 > 0:52:45Normally, we find these worms
0:52:45 > 0:52:49just growing as single individuals on stones or bits of shell.
0:52:49 > 0:52:53But in a very small number of places you get large numbers of worms
0:52:53 > 0:52:56settling together, growing on top of each other.
0:52:56 > 0:53:03'Those hard tubes are the building blocks of an underwater city and I want to see it.
0:53:03 > 0:53:05'Emily Venables is my tour guide.'
0:53:05 > 0:53:08- OK.- OK, good.
0:53:14 > 0:53:16And here we are.
0:53:17 > 0:53:23What's incredible about these tube worm reefs is there's just silt everywhere on the bottom
0:53:23 > 0:53:28of the loch here and suddenly you come across this little oasis.
0:53:28 > 0:53:32Inside these tubes is a creature much like an earth worm,
0:53:32 > 0:53:37but the only part you can see is its delicate fan of tentacles,
0:53:37 > 0:53:40used to filter food from the water.
0:53:40 > 0:53:44And the slightest disturbance causes them to pull back lightning fast
0:53:44 > 0:53:47into their hard tubes for protection.
0:53:49 > 0:53:53I love it when you just swim over them and it's like fireworks in reverse.
0:53:53 > 0:53:56They all just dart in very quickly.
0:54:04 > 0:54:07These shy little worms fashion their tubes out of the same hard
0:54:07 > 0:54:10material as other sea shells, calcium carbonate,
0:54:10 > 0:54:14but because they form vertical branch structures,
0:54:14 > 0:54:20they build up a reef where other creatures come to hide or hunt.
0:54:20 > 0:54:26There's so many things living here - we've got a hermit crabs, we've got anemones, we've got sea urchins.
0:54:26 > 0:54:30It's just a whole cast of characters living in this little city.
0:54:30 > 0:54:34It's absolutely brilliant, it's teeming with life.
0:54:34 > 0:54:38That's what we wanted to see, the scallop just swimming away.
0:54:38 > 0:54:42It's like a pair of comedy false teeth, isn't it?
0:54:42 > 0:54:47These are queen scallops, they're fascinating, they suck in some water
0:54:47 > 0:54:50and then they squirt it out really quickly - it's like a jet.
0:54:52 > 0:54:57There is a huge amount of marine life living in this one little spot
0:54:57 > 0:55:01and if it wasn't for the tube worms, there wouldn't be all these creatures here.
0:55:07 > 0:55:12Mooring boats and fishing are restricted in Loch Creran to protect the reefs.
0:55:15 > 0:55:18We should treasure our underwater worm city.