I don't think these activities are comparable. Saturation divers are regularly kept under pressures of 9 atmospheres, while astronauts in a space ship or space suit only need protected against atmospheres between 0 and 1. You'd never need something as rugged as a diving bell in space, and bends isn't even a risk. SciFi films often make it seem dramatic and fatal, but explosive decompression of a single atmosphere is survivable, as Kubrick accurately portrays David Bowman surviving such in 2001: A Space Odyssey.

In dark(if they are doing saturation there is no sunlight) with possibly horrible visibility. Any underwater work is pretty bad, but saturation takes it to entirely new level.