“might have to work “at atmospheric pressures similar to what a diver would experience,” the New York Times adds, and even spend “time in a decompression chamber” on their way back up to the surface, to find out.”
That’s cuckoo!! They’re not working submerged in a fluid (i.e., water). Its not unlike working deep in a mine.
I only know what I've read tonight about this project, but reports say that the operator has pressurized the tunnel interior to keep water from leaking in. That would have to be some pretty high pressure, so maybe the claim about workers having to decompress is true.
Air is a fluid. The word you're looking for is liquid.