The ocean water is usually good for natural hair. It's the chlorinated water that's the problem. When I last went to the beach (Atlantic Ocean, I think), I just got my hair wet in the ocean and then did a CW afterward. My hair felt great after being in the salt water.
Some people wet their hair and coat it with conditioner first, then hit the water. I don't think it's really necessarily if you're not going into chlorinated water, but it doesn't hurt.