The Shinkai (しんかい) is a manned research submersible that can dive up to a depth of 600 m. It was completed in 1970 and until 1981 it had the greatest depth range of any manned research vehicle in the Japan. The Shinkai is owned and run by the Japan Coast Guard and it is launched from the support vessel Otomemaru(乙女丸). Two pilots and two researcher operate within two high-strength low-alloy steel pressure hull. Three methacrylate resin view ports are arranged at the front and on each side of the vehicle.