This pool, close to Tokyo, has become our main pool for confined water training. It's just one stop from Atami, so fast to get to.
The pool has a shallow area (120cm) ideal for OW training, finning and lap swims. There is also a deep pool, about 4 meters, used for buoyancy training, rescue and advanced skills.
The pool temp is 29-30C, so always nice and wam; good for Fall through Spring training.
There are, of course, pools within Tokyo, but they cost 3-5 times as much for in-water time.