Okay Colton, it's only water, it's only water, it's only water...
You mostly just wish you had an extra bit of light. A lantern, a torch, a spell...something. You do hear rapids, and treading carefully so as to not slip and fall in the darkness, you make your way towards them. The sound seems to be coming in the direction of the only ambient light in the entire cave, so it's extra incentive. The air's not letting up its oppressive, choking mineral smell, and your breathing gets deeper to compensate.
Dropping down around a bend, the tunnel gets low overhead. You almost have to duck to keep going, and you're not especially tall to begin with. You feel the rock with your hand, steadying yourself; it's pleasingly rough to the touch, with lots of little holes and crevices for your fingers to fit in.
Things get brighter towards the end of the tunnel, but that's when you see someone half-buried and mummified among the rocks on the side of the room.