Mikomoto & Nakagi

The day starts with a call at the harbour, Shimoda or Nakagi depending on the shop, made on the morning after the skipper has read swell and wind, which is why divers who travel for this book several days rather than one. If it goes, the boat crosses open water to the rock and briefs underway, and everyone drops together on a single count. There is no easing into the site and no catching up: being slow off the ladder means missing it, and the group is spread across the blue within a minute of leaving the surface.

The dive is less swimming than holding on. You descend hard onto rock, tuck into the lee of a ridge and stay low out of the worst of the flow, gloved hands on bare stone or a hook set where the rock allows it. Depth stays moderate because the interest is in the water column rather than the bottom, and most of the dive is spent facing out into open water instead of down at the reef. When the flow is up, runtimes are short and the ascent is made in midwater with the boat tracking you.

The hammerheads come and go on their own terms. They pass in loose groups above and to seaward, sometimes on and off for an entire dive, sometimes as one column that crosses once and is gone. Around them the rock holds jacks, barracuda and dense schools of smaller fish, and something larger moving through on the current is always possible. Divers who fixate on the sharks tend to miss most of what is actually there.

Fitness counts here as much as logged dives: you will fin against water that does not let up, and holding a stop in midwater with nothing to hold onto is the skill that decides whether the day is enjoyable. Plan gas for the work rather than the depth. Early and late in the run the water heads toward 16°C and a hood or drysuit earns its place. When the rock is off, the same shops fall back to the sheltered coves and beaches of the southern Izu coast, unhurried diving worth planning in rather than treating as a consolation.