We are now developing a prototype underwater glider for long-term virtual mooring. It can land on the seafloor and remain inactive (sleep) there for a predetermined time to extend its monitoring period. If the seafloor is too deep, then it can sleep while drifting underwater. If it drifts because of the sea current, it will glide back to the designated area and remain there for more than one year. We have conducted a series of sea tests in the initial stage and confirmed its basic functions including landing-sleep, drifting-sleep, and heading control. To extend the maximum descent depth, we are also developing ceramic pressure-tight housings. Because of the high compressive strength of ceramics, we expect to be able to extend the maximum depth of the underwater glider to 6,000 m, which covers more than 98% of the world oceans. As described herein, an outline of the prototype underwater glider and sea test results is presented. An outline of the ceramic pressure-tight housings is also presented.