draining it at this point could be a mistake. If the ground around is very wet, you could float the pool out of the ground like a boat, doing thousands more damage to the structure.
IF there's no ground water or you must make repairs down there then you'll have to drain it, but you'll need something get rid of ground water, and that's more specialized than I am.

I think Al is right--the pipes to the pump look too thin, like maybe it's an automatic cleaner pump or a spa pump? I don't see an in-pump skimmer basket, which filter pumps always have, in my limited experience. Is that a pool heater or just the AC for the house?

I'm thinking the best course is to identify where the pipes go (Drains and skimmers, backwash drain, returns), get a new filter pump sized to your sand filter, and re-plumb it to suit. It's all PVC, so it's pretty easy to work, but only if you know what to plumb.

The skimmers and drains go to the pump, near its skimmer basket. It pumps water to the multivalve which can route it to filter and to the returns, backwards to backwash (and to the backwash drain), or directly to the pool, bypassing the filter.

Carl