The crocs are on the lagoon side so don't swim there!

I posted that because there is a curious "game" many tourists have decided to play - which is feeding a croc that hangs out by the road on the back side of the island. They actually BUY raw chicken breasts from restaurants to feed him!! It is a (BAD) accident waiting to happen!
Yes, you can swim with sharks & rays on some of the snorkeling trips. There is not a special area set up to swim with dolphins but you do often see them and can swim with them if you are lucky enough to be in the right place at the right time. You may see sea turtles but probably not.