Thunderball Grotto

Just off Staniel Cay, a small limestone islet has been hollowed out by the sea into a domed chamber open to the sky through holes in its roof. At the right time of day, sunbeams pour through those openings and light the water inside an electric blue, filling the cavern with shifting patterns while schools of sergeant majors and snappers circle the swimmers. It takes its name from the Bond film Thunderball, which shot here in 1965, and another Bond film returned decades later. Entry is a short swim through a low opening, which is why timing the tide matters.

What you actually see

• The light shafts - sunbeams through the roof holes lighting the water.
• The fish shoals - dense schools inside the chamber.
• The swim-in entrance - the low opening reachable at lower tide.
• The Exuma cays around it - swimming pigs, nurse sharks and iguana cays nearby.

When to go

Go at low or slack tide - at high tide the entrance is largely submerged and currents through the openings get strong. Midday sun gives the brightest interior light. The dry winter months bring the calmest boat conditions across the Exuma banks.

Honest expectations

This is a swim-through cave, not a walk-in one: confident swimming and snorkelling are needed, and currents around the entrance can be surprisingly strong on the wrong tide. Boat operators know the timing and it is worth trusting them over a fixed schedule. The grotto is small and can be crowded when several tour boats arrive together. Do not feed the fish, despite what some operators encourage.

Nearby

Staniel Cay, Big Major Cay's swimming pigs and the Exuma Cays Land and Sea Park.