Osekan Marine Service has been operating for over 50 years in Osezaki, one of Japan’s most renowned diving destinations. Our mission is to introduce the beauty of Japan’s nature and its rich marine life across all four seasons to divers from around the world, offering them an unforgettable experience. We take great pride in Osezaki being the best diving spot in Japan, conveniently located near Tokyo.

Now, in collaboration with Japan Airlines Vacations, Osekan Marine Service is excited to introduce this exceptional diving destination to more divers. Our facility is ideally located right in front of the Inner Bay, allowing divers to gear up and walk just 30 meters to the entry point. Our chief guide, Mr. Wakamatsu, is young but highly skilled and knowledgeable, specializing in guiding divers through Osezaki’s rare and diverse macro marine world. Together with his professional team, we are committed to making your diving experience truly worthwhile.

Explore Osezaki’s Four Seasons Underwater
Spring: A lush underwater forest emerges as seaweed grows densely, forming tunnels that stretch up to the surface.
Summer: The season of marine courtship, where you can witness various species engaging in egg protection and courtship rituals. The highlight is the breathtaking hatching of mouth-brooding fish during night dives.
Autumn: Many marine visitors arrive from the south, and visibility improves significantly.
Winter: The clearest waters of the year offer unexpected encounters with deep-sea creatures.

Best Diving Season: December to April
We highly recommend the winter diving season from December to April. During this time, deep-sea species such as anglerfish and ribbonfish may appear, and vibrant soft coral forests come to life. Blackwater diving is also at its peak during this season. Most remarkably, you can enjoy an unparalleled diving experience while gazing at the snow-capped Mt. Fuji.

Comfort & Facilities
After each dive, you can warm up in a hot tub (available on weekends from autumn to spring) while still wearing your wetsuit or drysuit, or take a hot shower at our facility. Due to high demand from both amateur and professional underwater photographers, we also offer extensive camera-related facilities.

Traditional-Style Accommodation & Dining
Osekan provides a unique diving and lodging experience with dive-and-stay packages. Our dinner plan includes exquisite Japanese seafood dishes, featuring freshly prepared local sashimi. Additionally, our chef’s Suruga Bay Cuisine is a special highlight, crafted with locally sourced ingredients. For those seeking a truly unique taste, we also offer exceptional game meat dishes.

Opening Hours
Regular: 08:00–17:00
Weekends & Public Holidays: 06:30–17:00
On Night Diving Days: Open until 21:30

Important Notice:
On the day of your dive, English support at the dive shop may be limited. We will provide guidance on what to expect for your dive. On-site, our guides will communicate with you using a translation app on land and basic sign language underwater, which will be reviewed before your dive.