YES!!! One of the best snorkling places left. If excursion goes to Goff Cay, it is the best spot. Drop off is many yards from where you snorkle. You can enter the water from the beach or be dropped off and snorkle to the beach. You will have a floatation vest, even if you are not that good of a swimmer.
There is also a GREAT group, EcoTours that you can get right at the dock in Belize and it goes to shark ray alley and to the reef with a stop at Caulker Caye.........WONDERFUL, did it last year and it is a great trip.
I've done the excursion to Goeff's cay, one of the best snorkeling trips I've done. I booked it right through Carnival and they picked you up at the ship, no need to tender into town and waste all that time. They also bring you right back to the ship, well worth it and highly recommend it.