What would the partial pressure of oxygen equal in an air mixture at a depth of 99 feet under water?

Question

Quizplus · Accepted Answer

At a depth of 99 feet underwater, the pressure increases by approximately 1 atmosphere every 33 feet. Therefore, at 99 feet, the pressure is about 4 atmospheres (1 atm at the surface + 3 atm from the water depth). The partial pressure of oxygen in air (which is about 21% oxygen) at the surface is approximately 159 mm Hg. At 4 atmospheres, this value is quadrupled (since partial pressure is directly proportional to total pressure), resulting in a partial pressure of oxygen of 636 mm Hg.

What Would the Partial Pressure of Oxygen Equal in an Air