musicgirl,
Dawn Beach is maybe a 10-15 minute cab ride from the cruise ship pier. The last time we went it was $15 each way (i.e. $7.50/person) for two people. I like this beach a lot. There's a little restaurant there and you can rent chairs, umbrellas floats, etc. The snorkeling is good when the water is calm. Occasionally, it gets a bit choppy, in which case we just leave the snorkeling gear on the beach and have fun in the surf.