Experts were stunned after a tiny rare sea creature usually living off Spain was found off Britain for the first time.
Babakina anadoni - a multi-coloured sea slug, measuring just 2cm in length, was captured on camera by Seasearch volunteer Allen Murray during a dive near Melledgan - an uninhabited rock island in the Isles of Scilly during The Wildlife Trust's National Marine Week.
This species is a member of the aeolid nudibranch family and has only been recorded a handful of times along the west coast of Spain and further south in the Atlantic.
Matt Slater, Marine Conservation Officer at Cornwall Wildlife Trust and Co-ordinator of the Seasearch programme for Cornwall and the Isles of Scilly said: "What an incredible find.
"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 it's 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, said: "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, often known as sea slugs, are soft-bodied marine animals that are famous for their extraordinary bright colours and striking shapes.
They are much like their land-based garden relatives and have a diet consisting of seaweeds, anemones and other sea slugs.
Sea slugs can incorporate the stinging cells from their prey into their own bodies giving them a defence against predators.
