Sounds like a fun way to practice deep scuba techniques - learning 'for real' in large water bodies is full of additional risks. However I'm a bit concerned at the 'caves' [not shown on the diagram]. Martyn Farr's book (http://en.wikipedia.org/wiki/The_Darkness_Beckons a rather short, blunt and to the point entry which makes sobering reading) makes it pretty clear that cave diving is pretty incompatible with long life (many people he talks about were killed on cave dives). Anyone I know who has done any sort of confined space dives has a terror story of things going wrong in even the most benign of holes. I think adding caves to the pool is a disaster waiting to happen - regardless of whether they are there to train techniques or not.