I don't believe I've ever been on board with that many but I'm sure the boat could handle it. The half day is aboard the Adventure, it's a 42' catamaran with a wide beam, plenty of room for everyone. They take you to the beach first where everyone gets comfortable with snorkeling for a little while (some people are first timers). Then they take you around to the reef where you snorkel from the front of the boat. Both of the Big Beard catamarans were custom built for snorkeling at buck island, the stairs were well thought out.