Although I have not used one for a submarine tank, nor have I any experience of sea water submarines, a pop bottles, I used the well known brown, tooth rotting, beverage containers, will certainly stand way more than the pressure generated by screen wash gear pumps, some years ago I made water powered rockets to amuse my children ( not myself of course
) and they were pumped up to my operating pressure of 110psi after burst tests burst tests were always over 150psi.
I've tested the Kavan 12volt pump at 48psi some time ago, that was fresh water though I cannot see why sea water would be different, suspended sediment might be an issue for the pump but a filter can deal with that, placing two pumps in series would yield an increase in pressure.
The 'emergency surface' system, triggered by a fail-safe, that I am building into my T Class Thrasher will use Robart r/c aircraft retraction system tanks, valves and lines. This equipment has an operating pressure of 110psi, so can well deal with the pressures of the water depth that model r/c gear can penetrate.