The UK is known for many things (rain, mostly), but exotic wildlife is not normally one of them. Although our terrestrial fauna may not be the world’s most diverse – or deadly – the same cannot be said for the creatures swimming in our seas.

Here are just a few of the fascinating species that call the UK’s waters their home…

1. Angel shark

You’ve probably never seen them, but that’s because they’re both exceptionally well-camouflaged and critically endangered, not because they aren’t actually there. Somewhere between a traditional shark and a ray, their rough, beige skin blends indistinguishably with the sandy sea bed, where they spend most of their time gliding around silently in search of flatfish and small crabs.

Once common off most UK coastlines, the shark is now exceptionally rare around Britain, as it is everywhere else. The next few years will be crucial in its uphill battle for survival.

2. Orange-clubbed sea slug

A tropical-looking beastie if ever there was one, this slimy-but-vibrant creature is a species of nudibranch, a large group of gastropod molluscs found all over the world and in every colour of the rainbow. Strange in the extreme, some nudibranchs are able to photosynthesize like corals, while others have detachable organs. You can look but you can’t touch – this sea slug uses poison to defend against predators.

3. Leatherback turtle

OK, you may very well have heard of the leatherback turtle, but did you know they frequent the waters around the UK? These monstrous marine reptiles are stalwarts of nature programmes and are generally seen breeding on the shores of Costa Rica, or cruising round the islands of the South Pacific.

Their wide distribution takes them most of the way around Ireland and the UK, while Wales holds the record for the largest leatherback ever observed. The animal, found in 1988, measured two and a half metres flipper to flipper and tipped the scales at 900 kg – the weight of a small car.

4. Mauve stinger jellyfish

The UK is not known for housing wildlife that will hurt you, but these sometime visitors to our seas can give a very, very nasty sting. A bluey-purply jelly cloaked in a hood and covered with reddish-brown warts, this exotic-looking critter sparkles along the water surface, appearing almost luminescent in low light. Keep your distance – its tentacles grow up to three metres long.

5. Ocean sunfish

Also known by their scientific name, mola mola, these giants of the ocean migrate to Britain’s southern and western shores during the summer months. The largest bony fish on the planet, ocean sunfish can reach three and a half metres in length and two and a half tons in weight, but are completely harmless to humans.

Delightfully weird, the ocean sunfish looks a bit like its back half is missing, and spends its days drifting lazily close to the sea’s surface in search of algae, plankton and jellies.