My client has an above ground pool that is full but is leaking in the bottom some where is there any thing I can use to patch it up that doesn't require me to purge the water ?

There are some underwater patches designed for just that. The trick is finding the leak. Pool stores advertise leak locating dye that pinpoints the hole. One would think snorkeling gear would be needed to apply the patch.

Leaks most frequently appear to be at the bottom but the leak could be just an inch below the water line. Once the water gets behind the liner it then makes its way down to the ground. Start by inspecting the obvious wall penetrations like the skimmer or the return. How much is it leaking, like an inch a day or what?

American Leak Detection specializes in that type of work. My son works for them.