Pleurobranchus membranaceus (Montagu, 1815)

June 1996.
At Loch Fyne on the west coast.
An individual 70 mm long, swimming in open water at 15 metres.
Nik 5 with 2:1 close up extension tubes and Ikelite 50 flash.

for more information about this species go to one of the links below
OPK - Opistobranquis Encyclopedia of Marine Life of Britain and Ireland sea slug forum