My husband and I went on the 2-hour afternoon Key Largo Princess Glass Bottom Boat. The ship crew were super friendly and knowledgeable about the sea-life, impact on the environment, and the history. Along the way (not just at the reef), we saw sea turtles, nurse sharks, tarpon, sting ray, snapper, jellies, and other small fish. Great experience - would highly recommend (though not for those who get sea sick easily).