Hokkaido and Northern Japan
Ice dive in Sea of Okhotsk, off the coast of Hokkaido.

Tokyo: Ogasawara Islands

Izu Peninsula and Ogasawara

Kanagawa: Manazuru

Kagoshima: Amami-Oshima Island

Okinawa
Open Coast Travel
Specializes in adventure tours throughout Japan encouraging it's customers to venture off the beaten track and explore Japan's more remote regions.
Tel 1: 866-OCT-DIAL
Tel 2: 310-433-6653