I just opened my pool and I noticed a protrusion in the liner of my pool. I had this liner installed within the last 3 years. It is a sunken above ground pool. it is concrete bottom with wood on the sides with a custom vinyl liner (very expensive!). The protrusion is on the bottom of the pool on the angle down to the deep end. I didn't really notice it in the past, so I think this may be new. It looks to be about 2-4 inches wide, but I haven't gone in yet to inspect further.
I am not really sure what it could be since this is a concrete bottom. I poked at it with my pool brush and it seemed pretty solid. I dont have any nearby trees that would be causing the issue with roots. When the company installed this liner they did some concrete work, nothing major but I think it was just to make it smoother for the liner. See links below for a couple of pictures.
IMG_0757 1_zpswucvvwqu.jpg Photo by dellapor | Photobucket
IMG_0756_zpscmf5spmt.jpg Photo by dellapor | Photobucket
Any ideas what could be causing this? I am afraid whatever it is is going to bust thru the liner.