At a 33-foot depth underwater, the pressure is 29.55 pounds per square inch. at a depth of 66 feet, the pressure reaches 44.4 pounds per square inch. at what rate is the pressure increasing?

D₂ = depth at final point of measurement = 66'
d₁ = depth at initial point of measurement = 33'

Δd = d₂ - d₁ = 66' - 33' = 33'

p₂ = pressure at final point of measurement = 44.4 psi
p₁ = pressure at initial point of measurement = 29.55 psi

Δp = p₂ - p₁ = 44.4 psi - 29.55 psi = 14.85 psi

Rate of Pressure change is:

Δp/Δd = (14.85 psi)/(33') = 0.45 psi/ft

(note: a positive sign here indicates pressure increase with respect to a depth increase)