The combat suit was not just an outfit to be worn. It had plenty of tools necessary for one's survival, and all would be incorporated into such a suit. An example was the night-vision goggles fitted into the facemask, the air-filter mask, et cetera. Meanwhile, there was a small tank of compressed air by his waist.
Normal people would think that the air tanks that divers carried on their backs would be filled with oxygen when, in fact, they were not. Having a pure oxygen tank was actually very dangerous, and it might even induce oxygen-poisoning; as such, these tanks would all be filled with the normal balance of air, and this was no exception.
Xia Fei's compressed air tank was not even half the size of a fist, and it could at most last him twenty minutes or so. It could only be used underwater for a short while. Any longer and he would need a larger, more specialized air tank.
*Splash!*
