[albert_dao]

Originally Posted by teevee

I do think it could be a sea hare. I think a major possibility is that it is Petalifera petalifera, which "...is known from records throughout the warm waters of the world."

http://www.seaslugforum.net/factsheet.cfm?base=petapeta

As for variation in size:



(If you have a hair algae problem...)

Right down to several species that top out at about 4cm in length.

http://www.seaslugforum.net/factsheet.cfm?base=seahlist

I had one of these fellow for a while: http://www.seaslugforum.net/factsheet.cfm?base=stylstri

Heh, and to think, that's just the tip of the iceberg. I remember reading several sources in literature citing sea hares up to 40" long. Not sure how big the one in the picture is, but from my best estimation, 40" would be just a hair (har har) bigger.