If you are looking for an amazing snorkeling experience, then book a ships tour to the Palencaar Reef - this place is amazing, the water is crystal clear, the current gently pushes you along so the snorkeling is almost effortless. We saw so many amazing sea creatures on our tour. This tour might seem a bit pricey but it is so worth it. You get an experienced captain and an experienced dive master who is in the water with you at all times, he will point out certain things for you to see.
The reason i say to book a ships tour and not do this on your own is because you have to travel a bit by boat to get out to the reef, and if anything should happen to your boat - mechanically - the ship will wait for you to return. If you book on your own and something happens and you don't make it back in time, the ship will not wait for you.