Taking all that has been written above and adding a few of my own, here's where I am at with ENF classification:
we already have accidental nudity ENF, caught or surprised ENF, complicit nudity ENF and forced ENF. All of these have non-ENF counterparts.
then there is:
1) obliged nudity or "contractural nudity" - any situation where a woman voluntarily enters a contract (bet, dare or other) with terms and conditions, or a game with rules, or otherwise is "obliged" to get naked in order to "win" or "lose".
2) timid exhibitionism, or "prove I'm not a prude" nudity. Whereby a woman voluntarily gets naked to prove she is uninhibited, even when she is not. One would expect ENF in these situations because she is trying to overcome her inherent shyness but often does not succeed.
3) regretted nudity - similar to 2, but with a more obvious, delayed ENF. A woman voluntarily gets nude and is OK with it for a while, but then due to unforseen circumstances, regrets it later after its already too late.
4) self conscious nudity - or "self exposed nudity" - a woman becomes self conscious, and through fidgiting to adjust her clothes or to check herself out, inadvertently exposes herself. Rare with/ENF. Anyone have pics?
5) nudity out of necessity - a good one I hadn't thought of. Some pics of this would be cool too. This would apply to any stolen clothes situation, for example, or a major wardrobe malfunction (after the initial oops).
6) subversive nudity - a woman who is tricked into being nude.
7) oblivious nudity - like 3 in that there is an eventual, delayed ENF. Otherwise, though it is an involuntary rather than voluntary situation.
Add these to the pile.
Question - what type of ENF is a skinny dip ENF? I think the closest would be 2) timid/shy exhibitionist or 3).
Klondike