ivanbranco
Verifiability "essentially means another mapper should be able to come to the same place and collect the same data". Everyone can go there and see it's a naturist beach. In the same page you linked there's "Map what's on the ground", I have been there, I saw there's a naturist beach, you as a local also say that is an "informal, unmarked place for nudist". Why shouldn't we map a naturist beach as a naturist beach?

nudism=customary is a value made exactly for informal places, otherwise they would be =yes.

Also I don't get how this naturist beach is a "temporary event or feature". 

I opened the note NOT to know if this was a naturist beach (I saw it with my own eyes), but to know from a local if I should map it as nudism=yes or =customary. Based on what you say, I think we should map it as =customary.