We did the Shark/Ray Alley tour with Coral Breeze (
http://www.coralbreezelimited.com). We had 5 people in my family, and about 12 persons total. We had a great time and swam with sharks and rays. We also snorkeled near the drop off of the second largest reef in the world.
I highly recommend CBL for the tours. They were very pleasant with our group despite our ship arriving late. We still got to do everything we wanted and arrived back in plenty of time to get the ship. They make sure of it.
Also, we had lunch on Caye Caulker as part of the package. My entire family, including the kids, really enjoyed the lunch and then walking around Caye Caulker. They don't have cars on the island, and so walking is a must, and enjoyable.
Check out CBL web site. You can view pictures and book online. It is the most stress free tour we have taken.
Hope this helps.
ZCruiseMan
Rhode Island