Answer:
Surviving high levels of water pressure, longer duration beneath water as you have more oxygen in a submarine than one has in a scuba tank, protection against both freezing and extreme heat.
Explanation:
The deeper you go under water, the more water pressure is pushing down on you. The equipment keeps you from being crushed.
Near the bottom of the ocean it gets 39 degrees F and if you cross over a hydrothermal vent, it can get to an overly toasty 700 degrees F.
