This tip is from Mike, one of our engineers. He’s probably helped you out in the forums! Mike says:

I just had a well pump replaced, and the tech had an interesting trick for insulating the motor’s power connections:  he wrapped them with several layers of electrical tape, then swabbed the tape with PVC glue.

The glue melts the tape and the surface of the wire’s insulation into a monolithic waterproof layer.  The connections survive for decades down a water-filled hole, so it’s a proven technique for adverse conditions.