Amami Ōshima

Operators split between the north, around Naze, and the south, around Koniya on the strait, and which end you stay at shapes the week. Boats are small, runs are short, and two morning dives is the standard plan, with dusk and night dives added on the sheltered side. The strait is the pressure valve: when wind or swell shuts the open coast down, crews move into the channel and keep diving, which is why the southern base suits anyone travelling on fixed dates. The nest dive is generally run from that end too.

The island dives as two different places. The outer coast is hard coral built into broad terraces stepping down over rock, well lit and reasonably open, with clean sand beyond the reef edge. The strait is the opposite: sheltered, siltier, low on relief, with rubble and sand bottoms that reward slow searching. Away from the deeper sand plains the profiles are shallow, and shore entries stay workable on days when the boats stay in.

The nest dive is what most people book for, and it is worth knowing what it involves. You drop onto open sand with no reference, follow the guide until a circle resolves out of the blue, then hold position well off the bottom, because one careless fin stroke flattens ridges that took a great deal of work to raise. The fish itself is barely a hand's length, which is the part that surprises people. Several circles may be in view at different stages, some sharp and freshly groomed, others already slumping, and whether anyone is home is luck rather than schedule.

It rewards patience and a longer stay more than a tight itinerary, since the calm windows come and go and typhoons through August to October can take out days at a time. Topside earns a rental car: the interior is subtropical forest, and the wildlife worth seeing, the endemic Amami rabbit among it, is nocturnal, so tours run at night, with access on some forest roads capped and guided. Infrastructure is thinner than Okinawa's and less English is spoken, so book with a shop that answers email.