What is the PPO2 of 100% oxygen @ -33 ft of seawater?

Answer 1

Partial pressure is the pressure of an individual gas in a mixture of gasses. Since you have 100% O2 the partial pressure is the same as the ambient pressure.

33 ft below sea level is 1 atmosphere of pressure

total absolute pressure is (2 x 14.7) 29.4 psi (2 atm)