Ascension Island

Diving here runs on the sea state rather than a timetable. Boats go out when the swell allows and stay in when Atlantic rollers close the landings, which can happen in any month; on those days divers walk in from the calmer coves on the northwest side instead. Runs are short because nothing sits far offshore, and the group tends to be whoever else is on the island that week, so dives get arranged the evening before rather than booked months out.

The island is young volcanic rock and it dives like it. Lava tongues break up into boulder fields, arches and short swim-throughs, and reef-building coral is sparse, so the stone stays black under encrusting growth and the colour comes from the fish. Sites sit between roughly 5 and 35 m with 20-40 m of visibility, and water of 22–28°C means a thin suit at most. Comfortless Cove, one of the walk-in entries, takes its name from its use as a quarantine landing for fever-stricken ships in the 1800s; graves still sit above the beach.

Ascension's entire exclusive economic zone is now a no-take marine protected area closed to commercial fishing, designated at the end of the 2010s and among the largest such closures in the Atlantic. Isolation did the rest: a high share of the reef fish are found only around Ascension and, in some cases, St Helena roughly 1,300 km to the southeast, and the shallows still hold predators at sizes that fished coastlines lost long ago.

It suits self-sufficient divers already making the journey for other reasons, with slack built into the plan for weather and flights. There is no walk-up dive economy to fall back on, so a blown-out day means a shore entry or a day off. Anyone drawn to fish density and open-water encounters will get far more from it than a diver hoping for coral gardens, deep wreck work or a packaged week of guaranteed tanks.