The ears, right! But, why not "sea rabbit"?
Sea hares are giant, slow-moving, sea-dwelling slugs. They like to inhale lots of seawater to puff themselves up. To deter predators, they release clouds of foul black ink when they feel threatened. They mate in big disorganized clusters and then lay strings of eggs like mad: at times their eggs are all over the place underwater. This one was about 6 inches long, although I've seen much larger. Actually, they sound a lot like the underwater equivalents of rabbits.