When permanently removing a light from an in-ground fiberglass walled pool how do you seal the hole?

I had a certified electrician remove light cut all the the wires and remove all wiring back up to the breaker box, then I had my pool guy put the whole light, burned out bulb and all back, into the niche, the way niche was made the screw hole did not have a hole at the end of the screw, in other Words the screw itself sealed the hole. The light is no longer usable, but I don't have an unsightly hole there either and do not have to worry about someone being electrocuted by faulty light. (When the copper plate holding the seal around the hole was removed, it broke into. I went to the lumber yard bought a shiny piece of galavanized metal, had it cut the exact shape as the copper plate with screw holes and all had my pool guy install it instead of the copper plate, lot cheaper than buying the copper plate at a swim supply store) Then I bought a solar powered light, no electricity at all to the pool, turn it on when I want a lighted night swim, and walla my pool can still be lit at night. Works for me so far. P.S. after I did all that I was told that I could have just had the shiny piece of galvanized metal cut the same as the copper seal except not cut out the inside hole where light goes, and would not have had to put the light back in niche. I prefer it the way we did it.

AND:: I bet you have a huge rust mark streaming down your pool walls from the galvanized metal! The copper plate probably broke in two because the water had been out of balance and very acidic. Would it not have been better to have used stainless steel. The screw alone would not have sealed the hole either. Water is supposed to get to the back of the light fixture for cooling purposes.