1996 Toyota Camry - Water in wheel well

rain water in rear wheel well

I presume you notice this when you open trunk.

Any recent damage or replaced parts to the Camry’s rear-light fixtures? Or rear marker lights? If so, maybe one of them didn’t get re-sealed properly. Open trunk and figure out how water exits the rain-water channel that goes around the trunk opening. It might be directed over the tail-lights. Clean that channel if it has any accumulated debris while checking.

Could be something else, but that’s where I’d start.