kind of the same thing happened to my father and me at apache lake about 8yrs ago (before he passed), we tied our 28" pontoon sideways to the beach, water went down over night, thougt no big deal it always comes back up during the day, 4 days later the boat was 12-15 off the waters edge, had to leave dad there (i had to go back to work), he dug trenches, used wood and his old 79 ford f250 4x4 and pushed the sum bitch back into the water, took him about 3 days to get it back into the water ( i think he was drinking and fishing more than anything), i have some pics someplace, i'll try to find them and put them up