HELP! Unknown pipe fitting in my poolNeed some help with an unknown "hole" fitting in my pool. We bought a house that came with a pool, but the owners had already moved and did not give us any instructions on operating the pool. A lot of it I had to figure myself. One thing that I have not figured out is this threaded opening towards the shallow end of my pool (see pictures).
The issue I have is that debris finds a way to build up in here and I need to know if this is something I can plug. I assumed it was something to maybe screw a pole in? Upon draining my pool and cleaning this out, it appears the pipe goes down deeper and may be a part of some piping system. I have no idea.
If someone recognizes this and could offer an explanation, I would really appreciate it.