It would be pretty simple.
Weld together lengths of pipe to form a straight peice of pipe long enough to reach from the bottom of the pool to a few feet above the roof.
Drill a few holes near the lower end.
Weld the lower end shut with a plug that is hard and sharp.
Attach a swivel fitting to the top end and a fire hose.
Trail a long fire hose .
This assembly should be carryed by a heavy lift helicopter, the pilot will be breifed as to what part of the roof is directly above the pool.
The pipe dangleing below the helicopter will be centered over the target and released from a hight that will ensure penetration of roof and whatever obsticles are above the pool.
When the pipe has poked thru the roof the hose that trailed behind on the ground will be snagged by soldiers rideing in a tank. they will attach even more hose untill there is hose running all the way to the beach.
ON the beach a fire pump truck will fill the hose , the truck will be manned by firemen who must be rotated frequently, if they can get a heavyly armored tank there the rotation need not be quite as fast.
If the pipe that reaches all the way into the pool is too heavy , then a shorter pipe that only dangles above the pool might still work, but it would have to have a cross piece that would stop it from passing all the way through and cutting the hose.
