Pump what ? Ask him to use his d..ck to pump lah.

Water leakage is a headache problem. Have to fix the source ,as water will always find a way to get to you no matter how you block it.

Pool in the ground is okay as any minor leakage is acceptable, nobody will notice. Also,if the ground water table is low, it will not have much pressure to squeeze into any minor defects.

Whereas for our bro problem, gravity is always there. Water will find you no matter what you pump.

Water can only goes down, never up lah.

That's not a pool lah bro. Just a small pond. I thought that was a skylight on other project you are on.

But again, your case it might hold as you are creating a leakage proof wall , just like an aquarium.