Isla del Caño

Drake Bay has no dock. Boats are pushed off the sand, divers climb over the side while a crew member holds the bow into the surf, and gear crosses in dry bags and bins. The same wet landing happens in reverse on the way back. Trips are normally two tanks in a morning, and the surface interval is spent on the boat rather than ashore, since going ashore inside the reserve is restricted and daily visitor numbers are capped.

The reserve splits into two kinds of diving. On the sheltered side, shallow rock and hard-coral gardens sit in easy depths with little current, and that is where check dives, newer divers and anyone shooting macro end up. The outer bajos are a different proposition: isolated rock towers standing in open water, worked by current and cut by sharp thermoclines, where fish stack on the up-current face and you spend the dive tucked into the rock rather than cruising over it.

Visibility is the gamble. The same tower can open right up in the dry months and close down to a handful of metres once rain pushes the Térraba-Sierpe outflow along the coast. Green water is not automatically bad news, though: the cooler, plankton-heavy water that comes with upwelling is usually what brings the rays and the big schools in, so the clearest days are not always the best ones and the best ones are rarely the prettiest.

Two humpback populations use this coast, a northern group broadly December to March and a southern one from roughly July into November, so the calendar has two whale windows rather than one and the second overlaps the wettest, greenest months. Most people dive here as part of an Osa trip built around Corcovado rather than a dedicated dive week; the site list is short enough that seven days would start repeating, and December into April brings the most settled conditions.