Glaucus atlanticus Forster, 1777

Glaucus atlanticus

sub-classs Opisthobranchia > order Nudibranchia > sub-order Aeolidina > family Glaucidae

Closley related to Glaucilla marginata, floats on the surface and feeds on Bluebottles.

Distribution =  circumglobal, temperate and tropical
Max size =  at least 40mm

more info at Sea Slug Forum      more pics at nudipixel