Is not the answer to this dilema not to purchase a submarine larger than the bath?
I live in a first floor flat, and with no access to any garden, so I am stuck with it, the powers that be want to replace my bath with a new shower and tray,but I said no way, I did not reveal why though!! Looking on the bright side, I have no mother in law, no granny, no wife, or children. (i never call them kids)kids are young goats, I dont know though, on second thoughts.
Would not a 10x6 garden shed sort out this problem, build your indoor pool at leisure, and store your subs as well, dont forget the granny proof lock!!
P.S. the smart thing to do would be, to use someone else's swimming pool, as long as you dont wake them up!!!