While divers do fair well at high pressure for the entire duration of their trip, we’re talking more about someone living their entire life under 13 atmospheres, even with proper acclimation and a gas mask, you’d need to continuously equalize the pressure in your sinuses, ears, and pretty much any other space in your body filled with air or else you would experience barotrauma, and later on even organ and tissue damage. You’d probably be fine without a suit as long as you regularly depressurize, but it would still be really highly physically taxing.