'Cave' trivia and fun facts

Too obvious

One of the characters comments upon the fact "someone might have been there (the cave) before". This is obvious well before he says it as there are clearly several signs along the rocks leading to the cave itself and the cave's entrance is covered what appears to be a heavy welded steel crating.

Fume before water?

It's extremely doubtful that an experienced cave diver would smoke before a dive. Doing so risks breathing difficulties during the dive and potential respiratory infections afterward.

Errors

Experienced cavers never use flares as: 1) There is the potential for flammable/explosives gases such as methane being present. 2) The flares would litter the cave, the spoiling future cave explorations for others.