Scuba Diving & Snorkeling
Panama Divers, based out of Portobelo, can put together a day excursion from Isla Grande (reservations required). On Isla Grande, there is the certified and locally run Isla Grande Dive Center (tel. 232-6994 or 6501-4374; www.buceoenpanama.com) that offers scuba diving and snorkeling, with lodging on the island or round-trip transportation from Panama City. All hotels and cabins on Isla Grande contract this company for diving and snorkeling. They also offer activities on Isla Coiba and the Kuna Yala Islands. The Dive Center has snorkel rental, too, for $6 (£3).
Beaches & Boating
There is no "day tour" center with a roster of excursions and set prices; instead, you'll need to hire a local boatman and negotiate a price. If you're staying on the island, your hotel can organize a boat tour for you with a local, or in a pinch you can find a boat and driver at the main dock near Cabañas Jackson, or at the pier in La Guaira. It's best to plan ahead and reserve a time with a local boat, but on slow days you shouldn't have a problem finding a willing captain. Also, check the pier at the Hotel Isla Grande, or check with the staff there to see if they have boat trips planned.
Day boat tours usually include a zip through a mangrove swamp and a visit to one of the offshore islands such as Mamey Island, a private island up for sale but still open to day visitors. There is a fine white-sand beach here with good snorkeling opportunities, but you'll need to bring your own gear. This trip can range between $35 and $50 (£18-£25), depending on the amount of time you'd like to stay on the beach (in the event that they drop you off and pick you up later).