0:00:02 > 0:00:05Strangford's tides are legendary.
0:00:05 > 0:00:06Billions of litres
0:00:06 > 0:00:08rush through the narrows every day.
0:00:08 > 0:00:12But there's a little-known corner of the lough
0:00:12 > 0:00:14with a similar story to tell.
0:00:14 > 0:00:17The Dorn Nature Reserve is a well-kept secret,
0:00:17 > 0:00:19where a salt waterfall
0:00:19 > 0:00:23cascades over kelp, just off the Newtownards to Portaferry Road.
0:00:23 > 0:00:28It's one of the best rockpooling shores in the country,
0:00:28 > 0:00:32and no-one knows it better than marine biologist
0:00:32 > 0:00:35and all-round naturalist Pat Boaden.
0:00:35 > 0:00:38Great sound. That's very spectacular, isn't it?
0:00:38 > 0:00:40That's a marvellous sight, isn't it?
0:00:40 > 0:00:44I don't know anywhere else in Northern Ireland or indeed Ireland
0:00:44 > 0:00:46where I've seen a marine waterfall like this.
0:00:46 > 0:00:49It's an extraordinary example
0:00:49 > 0:00:51of a tidal rapids,
0:00:51 > 0:00:54and tidal rapids are immensely valuable
0:00:54 > 0:00:57because they have very, very rich species diversity,
0:00:57 > 0:00:59especially of things that feed
0:00:59 > 0:01:02by filtering out particles from the sea water.
0:01:02 > 0:01:04Many of the creatures here
0:01:04 > 0:01:07are usually only seen by divers in deeper water.
0:01:07 > 0:01:12No matter where you look, Pat, there's life on the stones here. That's a great sponge.
0:01:12 > 0:01:15This is one of the brick sponge, or rust sponge.
0:01:15 > 0:01:17I think this is brick sponge.
0:01:17 > 0:01:22The little holes in it are where the water current comes out.
0:01:22 > 0:01:24There's sort of ingoing current that takes the food in,
0:01:24 > 0:01:27little minute holes that are too small to see.
0:01:27 > 0:01:29But then the currents come together
0:01:29 > 0:01:33and they come out through these bigger holes in the side.
0:01:36 > 0:01:38Look what we've got here.
0:01:38 > 0:01:42This, I do believe... is a native oyster.
0:01:42 > 0:01:45Of course, these days, you mostly get the Portuguese one
0:01:45 > 0:01:48which has a wrinkly shell, but this, the native one,
0:01:48 > 0:01:51is much flatter on one side than the other.
0:01:51 > 0:01:53If you turn it over and look here,
0:01:53 > 0:01:56you can just about work out how old it is
0:01:56 > 0:02:01because these series of rings are just about annual.
0:02:01 > 0:02:03So maybe this is 15 or so years old.
0:02:03 > 0:02:06I didn't realise they got as old as that.
0:02:06 > 0:02:09Oh, yes. I think the oldest one we ever found
0:02:09 > 0:02:11was something like about 70 years old.
0:02:11 > 0:02:15- 70 years old?!- It was about twice the size of this, really massive.
0:02:15 > 0:02:18You never know what you're going to get underneath these.
0:02:18 > 0:02:21- Indeed, you don't. - There's more sponge.
0:02:21 > 0:02:23- You mean down here?- Yeah.
0:02:23 > 0:02:28Well, you've not only got sponge, but look what you've got here.
0:02:28 > 0:02:30Just let me lift these off.
0:02:31 > 0:02:34There you are. Those are...
0:02:34 > 0:02:36two sea slugs actually mating.
0:02:36 > 0:02:39Those look like the sponge, and I suppose
0:02:39 > 0:02:41that's probably a strategy for that species,
0:02:41 > 0:02:43to look like something else.
0:02:43 > 0:02:44They're very difficult to spot
0:02:44 > 0:02:47cos they're often a very good match
0:02:47 > 0:02:50to whatever sort of sponge they're on.
0:02:50 > 0:02:54Strangford Lough is a very special place, and I think the longer
0:02:54 > 0:02:58you work in it and look at it, the more special it becomes to you.
0:02:58 > 0:02:59What's special about it?
0:02:59 > 0:03:01It's the scenery,
0:03:01 > 0:03:03the way the light changes -
0:03:03 > 0:03:04you've got this interaction
0:03:04 > 0:03:07between the sea and light and the water.
0:03:07 > 0:03:10You couldn't ask for anything more tranquil at the moment.