I'm from Australia and was puzzled with beach game for a very long time.
My technique is this:
- I find preferably a girl by herself. This is because everyone that goes to the beach alone has the same problems. Either, they want to swim and need someone to mind their stuff or they need to go to the toilet/get food/get a drink. Either way the problem is the stuff you bring when your alone. So you can use this commonality for virtually anyone who is alone.
- I walk up to her being open and friendly and using qualification. I say "hey you seem like a trustworthy person

Would you consider yourself someone that's friendly and trustworthy?" (everyone wants to believe their friendly and trustworthy) "because you look like someone I can trust my things with, while I go in for a swim, and I'll do the same for you". The girl understands your problem and if you come across as someone "normal" and not peakocking on the beach haha, she'll say yes.
- Then tell her she's a friendly and open person and introduce yourself