Lol at some of the suggestions on here:
Throw Ipad in the pool...who does it benefit exactly, to ruin a £500 piece of kit? Not only that, it's probably the kids entertainment for the flight home.
Show the women at the pool, that he took their photo....yeh, great way to start a huge fight in front of all the kids.
Put him on a plane home....pay a few hundred quid to send him home early, and achieve what exactly? And what if he doesn't agree to that? Which he wouldn't.
I would be very upset at this, I really would. Unfortunately, I'm not overly surprised that a 28 year old, who had been with the same woman for 8 years (so no real experience of other women), would do this. We all like to think that our Partners don't look at other women, but they're not blind, and if these women are topless, the guy must feel like a kid in a sweet shop. I know if I was at a pool, and some guys were bottomless, that I would find it hard not to look. I wouldn't take photo's and I wouldn't text a friend to say I'd like to shag anyone, but I might text a friend and mention in passing that the life guard was hot or something.
I think you're going to have to have this out with him, and ask him how he would feel if you had done the same, ie. sent pics of Dad's at the pool to your friend, with the caption "DILF". I'm sure he would feel just like you do.