How much does water pressure increase per vertical foot?

The pressure increase is dependent on density of the water. Pure water at 60F has about 27.78 inches of water column (INWC or INWG) per psi or approximately 0.43197 psi/ft. This is from memory; but it should be close.

Fresh water: 0.43 psi per foot Sea water: 0.44 psi per foot.

So, for each additional 10 feet of depth, figure about 4.3 to 4.4 psi increase in pressure.

You can calculate this yourself by using the fact that fresh water weighs about 62.4 pounds per cubic foot (pcf) and sea water weighs about 64 pcf. Divide those numbers by 144 (the "footprint" of one cubic foot, 12 x 12) and there you go.

It's interesting to note that this pressure is independent of volume or expanse. i.e. the water pressure behind a fresh water dam at 100 feet deep is about 43.3 psi regardless of whether the dam's reservoir is 25 miles long or 10 feet long. Depth and density are the only relevant parameters needed to determine pressure.

Dive pressure, however, would be the water pressure of 43.3 plus the air pressure above the water. So the net pressure on your ears & body would be 43.3 plus 14.7 (one atmosphere)totalling 58 psi,or about 4 atmosphers. That's four times our normal experience. Worthy of careful consideration.

Regarding diving - internal pressure inside ones body EQUALS the atmospheric pressure (14.7 psi). [Otherwise we would be squashed by the athmospere.]

Therefore, the net result is still dependent on depth ONLY - in example given it would be around 2.95 atmospheres.