I have an 18x32 Oval semi-inground pool (built into a hill... One side is level with the ground, other side is completely above).
It was installe less than a year ago, so still under warranty.
I few days ago we discovered a "channel" that has formed, presumably over winter, in the bottom. The liner sinks down anywhere from 1-3" into this channel. It is about 2" wide and runs about 25 feet along the length of the pool.
I already notified my builder, just waiting for someone to come out and check.
I would like to clarify that this is not a small dent from foot prints, I have some of those. This is like a river winding along.
Yesterday my husband and I got in and felt along it (most of it is relatively solid, slightly softer than the rest of the bottom). However, we found a couple spots where if you lightly press, you can tell the liner is not supported by anything! You can feel the sand in most spots but in the deepest parts it feels like a trampoline!
I have not noticed any water loss (only minimal from evaporation) so I don't believe there is a leak.
I'm new to pools but I'm guessing something is very very wrong?!