My dream recall isn't as good as it used to be, but here's what I remember.
There was a body of water, like a lake. The water itself was crystal clear. The bottom of the lake however was dirty looking. The people around the lake got really upset when I wanted to go in and wade. (It was very shallow at this point of the shore.)
They kept telling me it was dangerous, as if some creature were going to attack me. I looked around. I saw nothing dangerous. There were marks in the sediment, like straight groves. I wondered if an alligator had made them. (Now it seems to me they could've been made from boats)
A little further out there was a Depression in the bottom.
It looked like a wide trench had been dug. Since the rest of the area was shallow I thought of it as a swimming(pool)area.
That's all I recall, except I think this dream repeated itself.