These images were taken by Tom Ashton at St Andrews, Scotland. They are of a shell-less pteropod probably Clione limacina. The animal was about 7mm long and had small fins flapping at one end. Tom was freediving so the photos aren't perfect but still show the animal clearly. Pteropds are a group of molluscs that are free swimming, living in the water column generally near the surface. There are two broad types - those that lack a shell (order Gymnosomata) and those which have a shell (order Thecosomata). The species photographed here is shell-less.