Marine hotspots such as Rathlin are as rich as anywhere in the world, according to long-time scuba diver Joe Breen.
"When you dive in tropical waters, everywhere you go you get the same corals, the same fish, the same everything," he said.
"In our temperate waters there is a much bigger diversity of habitats and therefore species. What shocks people is when they find out we have sponges and corals in our own waters," Joe added.
These days he is a senior marine biologist with the DoE's new marine division.
"When I first started diving, Strangford Lough was fairly pristine but it's been recorded that damage has happened over the years through fishing. In other places some species have gone and others have come such as spider crabs.
"We're seeing more litter, more plastics and stuff like that. We get a lot of discarded stuff on the sea bed," he explained.
Joe said he hopes the thing he will be remembered for is the sponge that has been named after him – one of the 29 new sponges discovered at Rathlin a couple of years ago.