You can fix most pool leaks without draining.

Yes, you can – unless the leak is in the main drain line or the pool is a fiberglass shell that needs structural repair. For vinyl liners and concrete/gunite pools, underwater patching is standard.

Vinyl liners: use an underwater patch kit (they cost ~$20). Clean the area with a scouring pad, cut a patch larger than the tear, and stick it on. It works. Concrete/gunite: hydraulic cement or an underwater epoxy works fine. You have to find the exact leak first – use a dye test (squeeze food coloring near the suspected crack and watch it get sucked in) or get a listening device if it’s deeper.

Draining a pool is risky. The liner can shrink or shift, and the concrete can crack from hydrostatic pressure (groundwater pushing up). Unless you absolutely need access to a leak below the waterline that can’t be reached otherwise, keep it full.

Just don’t skip the leak detection – patching the wrong spot wastes time and money. Find it, patch it, move on.