When Cottonmouth loses his hat in the swamp, it lands "right-side-up" on the water surface. In the next camera shot, the hat is now "upside-down" in the water.
The hat is not upside down. It has sunk so that only the crown is above water, forcing Cottonmouth to reach underwater to grasp the brim.
At the 0:06:30 mark as Walt and Ross go up the stairs Ross is talking but his mouth is not.