Polycera quadrilineata (Müller, 1776)

18 July, 2004.
Weasel Loch, Eyemouth on the east coast. This animal was one of many hundreds seen, some with spawn, some mating, on the kelp, gulley walls and reefs outside during the dive from 6 - 12 metres in 13.5°C water.
Olympus 5050 camera in PT-015 housing and Nikonos SB 105 slave flash.

for more information about this species go to one of the links below
OPK - Opistobranquis nudibranchs of the british isles sea slug forum