Shiretoko Drift Ice

A diving day starts with an ice check. Crews look at where the floes have packed against the coast overnight, then decide between walking in from a beach at the edge of the pack or taking a small boat out to a workable gap, since wind can rearrange the whole shoreline between one morning and the next. Groups stay small, everyone is tethered to a surface line, and time in the water is short - two brief immersions with a long warm-up between them is a full day.

There is no reef to swim along; the terrain is overhead. The underside of the pack is ridged and grooved where floes have rafted into one another, and the bottom below is shallow and sparse, so navigation runs off the ceiling and the line rather than off features. What changes between sites is mostly how the ice arrived: loose pans drop light through in shafts, while a solid sheet closes the dive down to a dim vault and makes the tether the only reliable way back.

It rewards patience and a macro lens more than range. Depths are shallow and current slight, so the difficulty is thermal: dexterity goes early and free-flowing regulators are the standard equipment problem. Build spare days into the plan, because a bad ice morning cannot be fixed by changing site, and Okhotsk ice has been arriving later and thinner over recent decades. It slots into a wider eastern Hokkaido winter, with sea eagles at Rausu and cranes inland near Kushiro.