In my world, submarine technology and ocean exploration is highly sophisticated. A large sub can house hundreds of people in addition to smaller subs and they are used to travel, kind of like airplanes. They are also utilized in warfare. Much like paratroopers, there are soldiers trained to rapidly ascend from submarines in the deep sea and reach the surface in a very short period of time without suffering any ill effects. What kind of technology would be needed to make this possible?
Technology is about 500 years ahead of our current time (2021).
Some example of the technology used in this setting :artificial wombs that is almost exclusively used to birth the humans in this world. Gyrojet guns are the primary form of firearm, but large railguns are used for artillery.
This is an earth-like planet, but is not Earth. It is not an Earth colony, rather an alternative universe
The maximum they would ascend from is 3000M
The soldiers rapidly ascending are in a sort of half biological half mechanical mech
Ascent to the surface should take about 10-15 minutes
These soldiers ascend to the surface but they never leave the water
Stealth is desired on occasion, but is not always necessary