Yeah; you notice pressure changes easily when you skin dive, but you notice them mostly because of the compressive load on your lungs and the various air spaces in your head, which are full of air at surface pressure. If you go scuba diving instead, you won’t notice the load on your lungs anymore—the regulator delivers air at ambient pressure, not at surface pressure. You do need to equalize the pressure in your ears and facemask frequently as you go up and down the water column, since they’re set to ambient pressure every time you do so and that changes as your depth does, but breathing itself doesn’t get much harder as you go deeper.
(There are various other pressure-related problems that can crop up, though—nitrogen narcosis is the most important one at recreational diving depths.)
Depends on the gas mix and the application. The gas mixes used at depth in technical diving are usually hypoxic, since oxygen toxicity becomes an issue with ordinary air at an ambient pressure of about six and a half bar or depths of around fifty meters; heliox, for example, is usually around ten percent oxygen. On the other hand, it’s fairly common for the gas mixes used during the decompression phase of a technical dive to be richer in oxygen than air is, since that helps flush nitrogen out of your tissues.
This isn’t usually an issue for recreational divers, though, who generally don’t dive below forty meters and use pressurized air or, more rarely, enriched nitrox mixtures. At those shallower depths, you compensate for the richer breathing gas by breathing in a slower, more controlled fashion than you would on the surface, though this has more to do with conserving gas and controlling buoyancy than it does with oxygen issues.
Yeah; you notice pressure changes easily when you skin dive, but you notice them mostly because of the compressive load on your lungs and the various air spaces in your head, which are full of air at surface pressure. If you go scuba diving instead, you won’t notice the load on your lungs anymore—the regulator delivers air at ambient pressure, not at surface pressure. You do need to equalize the pressure in your ears and facemask frequently as you go up and down the water column, since they’re set to ambient pressure every time you do so and that changes as your depth does, but breathing itself doesn’t get much harder as you go deeper.
(There are various other pressure-related problems that can crop up, though—nitrogen narcosis is the most important one at recreational diving depths.)
One also needs a lower amount of oxygen in the breathable air.
Depends on the gas mix and the application. The gas mixes used at depth in technical diving are usually hypoxic, since oxygen toxicity becomes an issue with ordinary air at an ambient pressure of about six and a half bar or depths of around fifty meters; heliox, for example, is usually around ten percent oxygen. On the other hand, it’s fairly common for the gas mixes used during the decompression phase of a technical dive to be richer in oxygen than air is, since that helps flush nitrogen out of your tissues.
This isn’t usually an issue for recreational divers, though, who generally don’t dive below forty meters and use pressurized air or, more rarely, enriched nitrox mixtures. At those shallower depths, you compensate for the richer breathing gas by breathing in a slower, more controlled fashion than you would on the surface, though this has more to do with conserving gas and controlling buoyancy than it does with oxygen issues.