I can see how it can be weird, yeah, but a few of the general tips come to mind: first of all, she probably doesn't have many guys approaching her, or even eyeing her, because well, it's a "natural" thing to do. Second, remember that you're on vacation, so you're never seeing any of the girls again. I'd say definitely go for it.
Of course, don't look at her boobs while talking to her. That'll be weird, just act like she's wearing something.
Other than that, I wouldn't go for a direct opener (it'll be weird to tell her you think she has beautiful hair when her boobs are out there). Probably a situational opener or something, a short 5 minute talk, then "I'm new here and I'm looking for cool people to spend my night with, what do you say we go for a blablabla"