>>988556>iDubbbzMake sure you have lights, waterproof clothing, knife, pry bar, tomahawk, mask and eye pro...you don't want that nasty water splashing in your face and getting a disease.
if you are bringing a gun, make sure you have electronic hearing muffs that cut out, other wise your going to burst your eardrums shooting in an enclosed "indoor" place. Maybe use a crossbow if you don't want a gun.
All kinds of nasty things can be found in the underhive. If you run into Genestealers or Genestealer cults, it's best to kill yourself instead of being captured.