Dominica

Diving splits into two clusters on the sheltered western side. The south-west, inside the Soufriere-Scotts Head marine reserve, holds most of the operators and most of the named sites; the north-west around Portsmouth, Cabrits and Toucari is quieter and dived far less often. Boats are small and moorings sit close in, so a two-tank morning involves little travel, and centres tend to add an afternoon or night dive rather than stretch the day out at sea.

The terrain is volcanic rather than reef-built: black sand, boulder fields and steep slopes where coral and sponge grow straight over rock, with arches and short swim-throughs cut into old lava. Sites separate mainly by exposure. The sheltered bays collect sand and rubble and reward slow, close-in diving, while exposed points and the seaward edge of Soufriere Bay, itself a drowned crater, sit in moving water and put schooling fish alongside you.

Geothermal activity is not limited to the one site everyone photographs: warm sand and smaller gas seeps turn up elsewhere along the south-west shore, including the shallows off Soufriere village. The sperm whales are a separate outing rather than a dive. Boats look for them offshore on dedicated trips, in-water encounters are permit-controlled and limited, and nothing is guaranteed, so budget most of a day and accept the odds.

Newer divers manage in the bays, but the island rewards people who already have buoyancy sorted, because the better terrain is slope and wall where you hang beside the rock rather than settle on it. It suits close-focus photographers and travellers who want rainforest, rivers and hiking between dives rather than a resort strip. Anyone whose trip depends on big sharks or broad hard-coral gardens should look at other Caribbean islands.