[Torchwatch]

The movie and the 3 TV seasons are all done with actors.
They seem to take over a "closed" school during the summer holidays and make the whole thing in the time available.
The young actors start each project as able to swim, act and perhaps dance a bit and are trained in synchro from scratch during the season.
There are assorted bits of behind the scenes video on dailymotion etc. You can see them getting hypothermic during cold training sessions and hurt while learning how to build a human pyramid. You see them as the people they are not as the characters they portray in the stories.
It is interesting to watch the actors grow and mature during the course of each story, it is visible from episode to episode.

Remember that at the time the original movie was made Japan had gone through a period of bullying in schools initiated by teachers, carried on by students and resulting in the suicide of several children. Water Boys was an attempt to do something positive for the losers and drop outs who the system were failing, hence the drive for happy memories and no regrets.