To determine the pressure in a fluid at a given depth with the air-filled cartesian diver, we can employ Boyle's law, which states that the pressure in an ideal gas (held at constant temperature) is inversely proportional to its volume. At a fluid's surface, the pressure of the fluid is the same as the pressure of the atmosphere just above it, which we'll denote as LaTeX: P_{atm}P a t m. If the volume of air, which can be treated as an ideal gas here, in the cartesian diver decreases by 19% as it is lowered to a specific depth in the fluid, the pressure of the fluid at this depth, in terms of atmospheric pressure, is