That is a pretty pond. As a self-employed business person I learned many years ago that it did not make business sense to deal with friends or family. It ends badly for most people. You probably need to move on and get a pro to fix your pond. Get a written contract of what he will do and see if he will agree in writing to come back and fix it if it should leak within a year. Oral contracts mean nothing in court and if a person won't give you a written contract, drop him and find someone else. Good luck.
