if you contact a local pool company, you can have a actual steel walled pool built you your specs...they can do any shape you want...on ground pools are capable of being built above grade, but can also be built below grade too..it is stupid easy to add bulkheads where ever you want too. there is a tonne of different liners to choose from too...i am not sure how well a liner will hold up to the sandpaper like skin of a couple sharks though...only issue is you may need to have a bit of a concrete step poured around the base of the walls to keep them in place...and although i am not sure how, i am sure a viewing window could also be added...