What is the PSI at 1500 feet below sea level?

At 1500 feet below sea level, the pressure increases due to the weight of the water above. Since water exerts approximately 0.43 psi for every foot of depth, the pressure at 1500 feet below sea level would be about 645 psi (1500 feet x 0.43 psi/foot). Adding the atmospheric pressure at sea level, which is about 14.7 psi, the total pressure would be approximately 659 psi.