[dahdum]

Your body is primarily water so no pressure suit is necessary, but gas narcosis, high pressure neurological syndrome, and oxygen toxicity are all serious issues. You use different breathing mixtures like trimix or heliox to manage them.

Ascending is just as dangerous since you now have highly compressed gas bubbles throughout your body. There are different models you can follow to manage decompression, but it’s far from settled science. Both individual variation and situational factors can affect it greatly.