Pleurobranchus membranaceus (Montagu, 1815)

9 July, 2014.
Lephinchapel, Loch Fyne on the west coast. 
100 mm animal at 8 m. One of several and spawn between 8 - 6 m. Water temperature 12°C.
Sony α6000  in Nauticam housing, 30 mm lens and 2 x Inon D-2000 flashes.
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