0:00:34 > 0:00:36'There's more war time adventure ahead,
0:00:36 > 0:00:39'this time off the Donegal coast.'
0:00:41 > 0:00:43We're just leaving Downings,
0:00:43 > 0:00:46heading out on a beautifully flat summer sea into the wild Atlantic.
0:00:46 > 0:00:49We're looking for a U-boat that sank in the First World War
0:00:49 > 0:00:53and we're in the company of two technical divers.
0:00:53 > 0:00:57'Alan Wright and his wife, Freda, get a high from going deep.
0:00:58 > 0:01:02'We're charging more than 30 miles offshore to the U-89,
0:01:02 > 0:01:04'a wreck Al knows well.'
0:01:04 > 0:01:08For me, I'm into exploring sub wrecks and submarines around this area.
0:01:08 > 0:01:11Unfortunately, to get to the better shipwrecks,
0:01:11 > 0:01:14the ones in better conditions, you have got to start to go deeper.
0:01:14 > 0:01:18'We arrive on site blessed by fabulous weather.'
0:01:18 > 0:01:23Just put the buoy on there and we'll lie clear.
0:01:23 > 0:01:26It is a perfect day from a whole number of factors.
0:01:26 > 0:01:28To do this dive in this location,
0:01:28 > 0:01:31a wind was going to blow your plans away, wasn't it?
0:01:31 > 0:01:33That's right, you've got to have so many things right.
0:01:33 > 0:01:35We've got perfect conditions, plenty of light.
0:01:35 > 0:01:37The unknown is the underwater visibility,
0:01:37 > 0:01:39but it does look pretty clear
0:01:39 > 0:01:42so with a bit of luck the visibility will be good as well.
0:01:42 > 0:01:44Can't believe the weather, it's just...
0:01:44 > 0:01:45Well, it's incredible really.
0:01:47 > 0:01:49'The U-boat is 60 metres below us,
0:01:49 > 0:01:55'an extreme dive requiring skill, experience and technical know-how.
0:01:55 > 0:02:00'Freda and Al will breathe mixed gas - oxygen, nitrogen and helium.'
0:02:02 > 0:02:05IN SQUEAKY VOICE: Helium check, five, four, three, two, one.
0:02:05 > 0:02:06THEY LAUGH
0:02:07 > 0:02:10'It's used to beat the narcotic effects
0:02:10 > 0:02:12'of breathing nitrogen at depth.
0:02:13 > 0:02:17'Al's using a computer controlled life support unit
0:02:17 > 0:02:20'called a rebreather, programmed to deliver precise gas blends.
0:02:20 > 0:02:26'Critical because even oxygen can turn poisonous in the deep.'
0:02:26 > 0:02:27Tell me about the checklist.
0:02:27 > 0:02:30It's a 20-point checklist I've got to do before I get in the water
0:02:30 > 0:02:33for this rebreather because it is a life support equipment.
0:02:33 > 0:02:37I follow the checklist, turn the valves on when it tells you to
0:02:37 > 0:02:39and do the manual checks.
0:02:39 > 0:02:42It takes about five minutes or so, that's what I'm doing at the minute.
0:02:42 > 0:02:45'And as if he doesn't have enough to think about,
0:02:45 > 0:02:48'Al's going to film the dive for us.'
0:02:56 > 0:02:57OK, you're clear to go.
0:02:57 > 0:03:00It's going to take just about two minutes to descend
0:03:00 > 0:03:0560 metres down that shot line onto the wreck of U-89.
0:03:05 > 0:03:08But they only get 24 minutes down there
0:03:08 > 0:03:11before they have to come back up.
0:03:11 > 0:03:15And after that, it's a full hour, coming up slowly,
0:03:15 > 0:03:19stage by stage, back into fresh air and this glorious day up here.
0:03:19 > 0:03:24You can actually just see them disappearing.
0:03:30 > 0:03:31As soon as we get in,
0:03:31 > 0:03:35we start descending down the line towards the wreck.
0:03:35 > 0:03:37If there's current there, you might have to swim
0:03:37 > 0:03:40and work a bit harder to get yourself down the line,
0:03:40 > 0:03:43monitoring your gauges on the way down as well.
0:03:44 > 0:03:48You can see the whole wreck and that's just wow, really,
0:03:48 > 0:03:49that's just fantastic.
0:03:49 > 0:03:52Each time you do the dive, even though you might have done the same
0:03:52 > 0:03:55wreck ten times, it is completely different every time you dive it.
0:03:55 > 0:03:58You'll see different marine life, different visibility,
0:03:58 > 0:04:01different currents, it's just so different, so vast.
0:04:07 > 0:04:11She sailed from Germany on 5th January 1918
0:04:11 > 0:04:14to go and attack convoys in the north of Ireland.
0:04:14 > 0:04:19She was spotted on 11th February by a British reconnaissance aircraft
0:04:19 > 0:04:23and they basically homed in the destroyers to search for her.
0:04:23 > 0:04:28She actually surfaced in daylight on February 13th 1918,
0:04:28 > 0:04:30right next to HMS Roxburgh.
0:04:30 > 0:04:32And Roxburgh spotted her
0:04:32 > 0:04:34and basically rammed her just after the conning tower.
0:04:34 > 0:04:38You can see the engines just sitting out there, the twin diesel engines.
0:04:52 > 0:04:57Swam forward to the conning tower and it was full of primrose anemones.
0:04:57 > 0:04:59It was covered in anemones, of every colour you can imagine,
0:04:59 > 0:05:03just like a carpet really, everywhere.
0:05:03 > 0:05:06We can see the conning tower hatch open, and the periscope standard,
0:05:06 > 0:05:09where the periscope went up and down.
0:05:29 > 0:05:32Then we dropped round the side of the conning tower with the current
0:05:32 > 0:05:35and drifted slowly down to the deck gun.
0:05:35 > 0:05:39The deck gun there is a 105 mm deck gun that was used
0:05:39 > 0:05:45really during the war, they would surface and shell the convoys.
0:05:45 > 0:05:47You see the gun sitting on top, just pointing,
0:05:47 > 0:05:50almost ready to shoot really and you can just imagine, you know,
0:05:50 > 0:05:53that these guys have gone away and they're going to come back later.
0:05:53 > 0:05:55It's just incredible really.
0:05:57 > 0:06:01Then we went to the torpedo loading hatch, and we looked in.
0:06:01 > 0:06:04That hatch is at an angle to get the torpedoes in
0:06:04 > 0:06:06because they're six metres long.
0:06:06 > 0:06:07Lo and behold, down there in the bottom
0:06:07 > 0:06:09you could see the two torpedoes,
0:06:09 > 0:06:11lying there with the fins and the propeller.
0:06:14 > 0:06:17That thing was designed for one purpose - to sink ships.
0:06:17 > 0:06:20Those torpedoes just bring it home to you,
0:06:20 > 0:06:23and a crew of 44 drowned in that vessel.
0:06:32 > 0:06:36We're out here in the blue wilderness far from the shore,
0:06:36 > 0:06:38and the divers, by my reckoning,
0:06:38 > 0:06:42will just have ended their dive and be heading up for the surface.
0:06:42 > 0:06:44It's kind of a privilege being out here
0:06:44 > 0:06:48because most people back there on land will never get to be
0:06:48 > 0:06:5232 miles from the shore in a very small boat,
0:06:52 > 0:06:55and to spend the day in the company of people who...
0:06:55 > 0:06:59I suppose they put their life on the line in search of adventure.
0:06:59 > 0:07:00It's quite something.
0:07:03 > 0:07:07'This is perhaps the most dangerous time, ascending from the deep.
0:07:07 > 0:07:10'They must stop and wait at stages
0:07:10 > 0:07:13'to avoid every diver's worst nightmare - the bends.
0:07:13 > 0:07:17'To avoid it, Al and Freda must get rid of the nitrogen
0:07:17 > 0:07:19'that's been stored in their blood stream,
0:07:19 > 0:07:20'and that means hanging around,
0:07:20 > 0:07:23'breathing oxygen-rich air nearer the surface.'
0:07:29 > 0:07:31There they are.
0:07:31 > 0:07:32Back up from the deeps.
0:07:32 > 0:07:34They look happy.
0:07:37 > 0:07:39Good dive, Al?
0:07:39 > 0:07:41Yes, very good.
0:07:41 > 0:07:44A little bit dark, but not bad there at all.
0:07:44 > 0:07:45What's the light penetration on the wreck?
0:07:45 > 0:07:48You're talking about 200 feet down?
0:07:48 > 0:07:51Yes, 200 feet down you're getting natural light down there.
0:07:51 > 0:07:52It's pretty good really.
0:07:52 > 0:07:56It's about 15 metres, about 50 feet, is all the visibility.
0:07:56 > 0:07:59Whenever you're in the office or doing stuff
0:07:59 > 0:08:02that you don't want to be doing, is this what drives you?
0:08:02 > 0:08:05- Oh yes.- Yes, absolutely.- Definitely. - Especially days like this.
0:08:05 > 0:08:07The amount of ship wrecks we've got out here,
0:08:07 > 0:08:10when we get the weather like this, it's world-class diving out here.
0:08:16 > 0:08:19Subtitles by Red Bee Media Ltd