Answer
1.2m.
Work Step by Step
The pressure difference is due to the depth of water.
Use equation 10–3b, and round the answer to 2 significant figures.
$$\Delta P=\rho g \Delta h $$
$$\Delta h= \frac{\Delta P}{\rho g}$$
$$=\frac{(85 mm-Hg)((133 N/m^2)/(1mm-Hg))}{(1.00 \times 10^3 kg/m^3)(9.80 m/s^2)} \approx 1.2m$$
His maximum depth would be about 1.2 m.