1. The problem statement, all variables and given/known data How does the pressure at a point in a fluid vary with the depth of the point below the surface of the fluid? A bottle, full of air at atmospheric pressure, whose volume is 500 cubic centimeters, is sunken mouth downwards below the surface of a pond. How far must it be sunk for 100 cubic centimeters of water to run up into the bottle? 2. Relevant equations 3. The attempt at a solution I know that the deeper that point is placed in the fluid, the more pressure it experiences and the greater depth the bottle is lowered, the greater the compression. I know we're looking for the depth at which 100 cubic centimeters of air is replaced by 100 cubic centimeters of water but not sure how to proceed. Do I need to find the pressure of the bottle first? P=rgh but rearrange to find height/depth H=P/rg ?