I have a wide mouth skimmer and a closing plate that I have yet to completely seal going on 4 seasons now. I’ve tried the foam inserts that wedge into place and they don’t work. I use a self draining cover so I need the water level high so the water on the cover will flow out the return jet. Is there a silicone that cures under water I can use with a cork gasket to make a leak proof seal and finally get a season where it doesn’t leak? Any suggestions would be helpful.