In this training, the hands and legs are bound and they have to jump into the 33 metres pool to "swim" 3 laps of it.
It is not actually to "swim" as they had to make bobbing and arching movements to stay afloat and keep moving.
When the end of each lap is reached, they have to do a forward or backward somersault.
After the 3 laps, they have to get to the bottom of the 4 metres pool to get their mask with their teeth. The instructors are not unreasonable to make them wear it.
There has been suggestions to use paper rope or Velcro tape so that it can be broken in cause of emergency. But this is not allowed as it would be bad psychologically and the divers would think that it is only for show.