Quote:
but after thy went on their towels to talk I couldn't figure out how to go to them and initiate a chat or something.
So there's just her and another guy - thats a set of 2 which shouldn't be that hard to communicate with.
I think you should write 4-5 openers / conversation topics for these kind of situations (mixed sets) and remember them and use them in this kind of situations (when nothing else pops in mind).
For example, you could've asked them "how do they know each other?", "are you best friends?" - then run the best friends test if they are, "how long they're staying, etc". Just keep the group opened, and focus more on the guy and not the girl.
It would've helped if you had another guy with you but since that wasn't the case the best thing to do I'd say is to focus on the guy/group, at one point tell them you have to go soon and before you go, try to schedual another beach hanging out if possible.