You’re generally on the right track, just off slightly. In the scuba diving world 1.4atm partial pressure of Oxygen is generally considered the maximum safe par

You’re generally on the right track, just off slightly. In the scuba diving world 1.4atm partial pressure of Oxygen is generally considered the maximum safe partial pressure when working (ie swimming). 1.5 atm for rest. This makes the depth limit for regular air to be 216 feet. Though there are a lot of divers who dove deeper than that befor trimix became so common.