“What an incredible find!” said Matt Slater, Marine Conservation Officer at Cornwall Wildlife Trust and Co-ordinator of the Seasearch programme for Cornwall and the Isles of Scilly.

“We were extremely excited to hear about the sighting of this colourful nudibranch – a species that we believe has never been recorded in the UK before.

“It’s one of the prettiest sea slugs I’ve seen and, given its less than half the size of your little finger, it’s amazing Allen spotted it at all! There’s still so much out there that we don’t know about our marine environment. Records like this from our Seasearch divers are vital in helping us understand and better protect our seas.”

Lucy McRobert, Communications Manager at Isles of Scilly Wildlife Trust, added: “We never cease to be amazed at the wildlife turning up in Scillonian waters. From rare and beautiful nudibranchs to violet sea snails to great whales like humpbacks and fins, every time we dive beneath the surface we learn and see something new!”

Nudibranchs are soft bodied and often brightly coloured. They feed on seaweeds, anemones and other sea slugs, and can take the stinging cells from their prey and incorporate them into their own bodies, offering a defence against predators.

To find out more about becoming a Seasearch volunteer diver, visit www.cornwallwildlifetrust.org.uk/seasearch

Main image: the rare and multi-coloured Babakina anadoni recorded in UK waters for the first time/Credit: Allen Murray