Gorgona Island

Nobody drops in on Gorgona on a whim. The journey eats most of a day at each end, so visits are sold as multi-night packages rather than day trips, and everything is arranged well in advance: park entry is capped, the single small lodge houses everyone on the island, and diving runs as a couple of boat dives a day from the beach in front of it. There is no second operator to switch to and no easy way to add a day once you are there.

Underwater this is rock first and coral second. The mainland-facing side carries the reef, low stands of branching coral growing over rock in easy depths, while the exposed side is steeper stone with more swell and more water moving through it. Gorgonilla and the offshore stacks are the first things the weather takes away, and losing them for days at a time is routine rather than bad luck; a rough week shrinks the plan back to the sheltered sites near the lodge, where the shallow diving sits anyway.

Rain shapes the rest. This coast is wet through most of the year, runoff and plankton keep visibility modest, and February through April is the better bet if clarity matters to you. From July humpbacks move in to calve and their song carries through the dives, holding into October; hammerheads pass through often enough to be worth mentioning and rarely enough that planning around them is a mistake. Between dives, guided walks lead through forest that has closed back over the old prison blocks.