Question 1: How long is too long?
Comment 1: I'm not sure about this, but do boots rust in water? I sort of remember but I can't be really sure about whether I'm remembering right. If so then in the 'boots take damage from danger zones so you don't' way it makes sense. This doesn't take into account the 'erm, but the water's not *that* high!' aspect, though (I see the current water as reaching up to maybe knee level, if not merely ankle-level).
Comment 2: On the other hand, this could lead to a new trait that helps you resist dangerous floor damage/bleeding. But such a trait would have balancing/relevancy issues....
Comment 3: Also, I've only played the first level of the original Doom but the water there was poisonous (>_> but it probably wasn't really water either... probably actually acid).