tank
When Eddie wants to come out of the cylindrical tank, he needs Arthur to unscrew the heavy steel lid, so obviously the lid was screwed down after he went into it. Maybe this all looks kinda cool in a movie, but would you want to go into a tank like that? Wouldn't you choose instead one that you could exit when you wanted, in case Arthur has dozed off or gone to grab a burger (or left for the weekend)?
"I beseech ye in the bowels of Christ, think that ye may be mistaken."