I just put up an oval above ground pool a few weeks ago, and i did all the work myself. Everything is going really well so far. But there is one place under the liner at the bottom of the pool where a sink-hole developed after the pool was filled for a couple of days. Its been there for a couple weeks now and so far hasnt gotten bigger. The hole (dip) is circular, about 4 inches wide, and I'd say about 3 inches deep. At the top edges of the hole, it just kinda drops almost straight down, so the shape of the hole is almost a mix between a soup can and a bowl. If i push around in the hole, at the bottom i can tell that its not solid, the liner gives some, so the sand underneath has apparently sank even lower but the liner is stretched as far as it will go (for now). Should i be concerned about this? The liner is brand new, so i obviously want it to last for years. Its an oval pool which has the metal supports that go under the pool which get covered in sand. The hole looks to be near the end of one of the supports. So i'm thinking I didnt shove enough sand at the end of that metal support where the band attaches to the support on the opposite side. Either that or some of the sand around that end of the support somehow got pushed into the support itself when the pool was being filled (metal support is long and rectangular, with a hollow middle thats opened at the end). Either way, I'm not sure what I should do about it. Should i be concerned? I can deal with it looks-wise. I just dont want to have to replace the liner after 1-2 yrs because I decided not to do anything about it.