I have a 18x33 AG that was here when we bought the house. This is my first pool and I am learning a lot on this forum. My problem is the sand has been washed out from under the liner directly below the skimmer. It goes about 4 inches back and is about a foot long across. How do I go about fixing this? Do I need to drain some water so I can lift this area up and replace the sand or is there another method? Maybe pulling it back with a plunger or something?

Thanks in advance.