Mystery Acquatic Animal

I may be in the wrong place but I saw a strange aquatic animal that someone thought was a snail and I was curious if someone can help me identify it. Last week we were in a marina near West Palm Beach,Florida. It was 9pm and we saw what at first looked like a blob of oil (black with no apparent organized shape). Then the shape started swimming using barely formed wing action. there was a small pencil shaped "head" structure. That was all that I could identify in its amoeba like movement.

Can anyone help me?

Ben

If saltwater I would have to guess nudibranch. It is a sea slug, is quite beautiful, and comes in many colors and varieties.

I think Megan is correct. Of course, it could also be a genetic mutation caused by ocean pollution and destined to eat tall buildings and star in a corny monster movie called "The Giant, City Eating Slime Slug From the Deep." Well, maybe not.

I also have to agree with Megham, but I have to give John a thumbs up for creativity!!