I just wanted to give a big thumbs up for Frankenplugs for solving pool leaks in returns. (https://www.amazon.com/s?k=frankenplug&crid=1VV61J9Y6W1AR&sprefix=frankenplug,aps,75&ref=nb_sb_noss_2)
My fiberglass pool had been losing about an 1" every other day all summer. I bought a leak detection...