Usually all you need to do is raise the water level in the pool as high as it will go without being above the top of the skimmer and wait. As long as the liner doesn't shift position everything will go back to normal fairly soon. If there is a lot of water behind the liner, to the point where you think that the liner might shift soon, fill the pool right to the top, even if that is above the top of the skimmer.
Water behind the liner means the local water table is above the water level in the pool.
1. As Jason said the water table is up, just raise the pool level up and wait a bit. For those with habitual floating liners, never drain the water down till a day or two after the rain storm to give the table time to settle down.
2. You have a leak. Find it and fix it then wait for it to drain away. Last year my liner started floating for the first time ever. We actually unzipped the liner in 1 corner for a couple of feet and then pumped the water out from behind the liner and put it in the pool. The next day the liner was floating again so we knew we had a leak. After days of searching I couldn't find the leak with the liner floating, so we pumped the water out from behind the liner again and this time the cut in the liner showed up quite well because the water pressure was forcing it open.