Diving in Hokkaido mostly happens at the Shiretoko Peninsula that protrudes into the Sea of Okhotsk and in Lake Shikotsu which is in the town of Sapporo. Ice diving is certainly not for the faint-hearted but it is rewarding and a very unique experience.
Diving in Lake Shikotsu, a caldera lake, is another interesting experience as the lake is known as the clearest lake in Japan. Most of the dive operators can be found at the west side of the lake and it is possible to dive there on a year-round basis as the lake does not freeze over during winter. A good time to pick is during salmon season where you can see spawning of red salmon which have made their way upriver into the lake.
The Shiretoko Peninsula is a UNESCO World Heritage Site and diving usually takes place in February to March when the sea ice is just beginning to break up and ice floes appear off the coast of the peninsula.
A basic open water certification is sufficient but there is likely to be a strict brief about procedures and safety measures before diving. Donning a drysuit, you are likely to dive for less than half an hour and only go as deep as 49ft (15m) as water temperatures are below 37˚F (3˚C).
Visibility underneath the ice floes is about 66ft (20m) and on a bright sunny day, the underwater scene is surreal with the sunshine penetrating the ceiling of ice and cute little cliones, or sea angels, flittering about.
Use the train networks to get to Sapporo or take short internal flights from within Japan. There are also international flights directly to Sapporo from Hong Kong, Malaysia, Taiwan, South Korea, China and also Russia.
From Sapporo, there are trains to get you to the Shiretoko Peninsula and driving is also an option.