You set-up the two umbrellas by planting them next to each other when the water gets to be a couple of feet deep. then, swim under your ghetto makeshift island shack with a six-pack of beer, and start chugging.
There. If people at the beach curiously point at you and are, like, "WTF??" Then, and only then, you've got yourself a genuine Polish Beach House. Make sure to snap a photo to send to Polish Beach House Magazine. If you're lucky, you'll make next week's cover.
If you add 2 more umbrellas, it becomes a Polish Beach Duplex. More than 4 total umbrellas makes it a Polish Beach Mansion.
LEEBO: Relax, Lester. We'll set up a Polish Beach House down yonder and you'll be good to go