We are on the SOS in September and we booked a snorkle tour with Stewart's Cove. It's not through the ship. I've read some positive posts about the company and it sounds like fun. If you go to their website one of the three stops they make on the snorkle dive is they feed sharks on the bottom of the ocean if you dare to be on the top of the water. My husband is going in, I don't know if I am.
One other thing I liked is that they pick you up at the Pier early about 8:00 and you get back around 1:00 so it still leaves plenty of time for other things.