Danno, Wet your boat down with hose or sponge, then take a sponge soaked in soapy water,( I used dish liquid ) and go over any areas that might have leaks.Do one hull at a time. Take a vacum cleaner, reverse the hose so that it blows instead of sucks,hold the hose about an inch from the drain plug hole, and then look for where it's blowing bubbles/foaming, these are your leaks! To check the seal of the drain plugs you can put the hose in an inspection port if you have one, and soap up the closed plugs. It's easier if you have two people, and helps if you have a grease pencil to mark the leaks.