You've got very limited option; the only SURE fix, involves excavation.

A drain snake is a BAD idea. Plumber's augurs work with DWV fittings that have sweep turns, not pressure fittings that have hard 90 deg. turns. DWV fittings are *rarely* used on pools (should be: are never used!). Using an augur on a pressure fitting can damage the fitting or 'stick' the augur irretrievably (back to excavation!)

You can use a 'blow bag' or 'drain bladder', like this:
G.T. Water Products 186 Drain King Unclog Hose Attachment
but be careful. If you over pressurize the line, you can break it.