I'm very relaxed about porn, strip clubs, lap dances etc but I would have a significant issue with this. There would be no "is this the time or the place". My husband would be left in no doubt how perverse this was and how pissed off i was.
You see these men on holiday, peering over their sunglasses watching you, or pretending to play with their phones and watching you, or pretending to read their papers and watching you instead. They make me feel really uncomfortable and I feel sorry for the wives when they are married to letches. No way they don't know it. But to take pics is something else entirely, I'm not sure I would end my marriage over it, but it would absolutely change my view of him and would be a major issue.
The other point to note is, if he is doing this when you are with him, what's he doing when you aren't there, it speaks volumes about who he is.
Would your reaction change if he was caught photographing these women? By them, by their partners, by hotel staff? Because if you're only thinking "now is not the time" because no one else knows, then that also says something about you, I'm sorry. My reaction would be the same, whether he was caught or not, and it would be immediate and extreme.