What a great trip/visit to the fort. The boat leaves early, 8am and returns about 530. Breakfast and lunch are provide on the boat and is very filling. No need to take extra food. Would suggest you take the tour on arrival at the fort & then go back to the boat for lunch. At lunch you could also pick up some extra water for the rest of the day. There is no food/drink available to buy at the fort. The tour is very well done by knowledgeable guides. If you have time, try a bit of snorkeling. You don't need to bring your own gear, it is all provided by the tour.