It sounds like you're in the water on the other side of the water wheels. What you need to do is to get to the edge and then climb out of the water. It's possible to do, albeit a bit tricky. Try looking up, moving forward, and jumping at the same time. Keep holding down the forward key, and with luck, you'll soon be on dry land again.
It gets frustrating for me on occasion because when I'm in deeper water (like where you are
), it seems that after I jump, I fall way down below the water and can't climb out. But eventually, you can.