We have a 30' concrete spillway, 25 years old, that regulates a 54 acre lake. With current drought conditions we are able to identify a small leak at the bottom of the spillway. Good news is that the Dezurik 24" butterfly valve is not leaking. We have a very small diameter concrete area that is leaking. We would like to repair with an epoxy product such as System 3 Submarine underwater epoxy or possibly a Sika equivalent. Working depth of repair will be 26' underwater...I have pictures but am unable to post due to my low tech aptitude...Any ideas on best product to use?