Snailish thing?

[Coll]

This was seen around 30 feet at Breakwater in Monterey, California. I only got one shot because I was dragged off to see something else. The antennae tell me it's not just a white sponge of some sort and it was moving, albeit very slowly. Any ideas? Sorry it's not a very good shot.

 

[LeslieH]

You're right - it's a snail, Lamellaria diegoensis. They get mistaken for nudibranchs a lot.