Live well flooding boat ?? how to fix

[Florida85]

I have a 85 20ft master angler. It has the livewell in the back of the boat in the hull (you walk over it). If you are not underway it overfills with water due to it being below sea level. Water pushes through aerator. I have tried everything. It literally floods back of boat with ankle deep water.

The problem is the water is getting pulled from a through hull on the bottom of the boat. Its a connection where I cannot plug.

Has this happened to anyone else? What did you do to stop it?

Thank you.

Justin