Okay, you're placing towels on a beach from left to right, trying to match patterns while not going out of bounds (since no one appreciates a wet towel before they wet it themselves). If you place on an umbrella, you get some kind of bonus — and this image shows two umbrellas scored in the left-hand column despite only one umbrella being covered. Whoops, error! Maybe this image can be fixed prior to production. Anyway...
If you see this image:
Then you probably understand that you're going to "buy" towels at a cost of 0-2 sand dollars, with towels sliding into the cheaper slots over time.
For those who want all the details on this Q3 2022 release from designers Frank Crittin, Grégoire Largey, and Sébastien Pauchon — the team behind Botanik, Ankh'or, and The Way of the Bear — check out this description that fills in many of the gaps created by a picture-only explanation:
In the game, you have your own beach board with room for 13 towels, the board has seven rows in which towels can be placed, and during set-up, you randomly place eight umbrellas in designated locations on your board. Each player places one random towel in the leftmost column of their board; each towel has three different patterns on it. Place six random tiles in the two rows of the market and one sand dollar in each row.
On a turn, either take all the sand dollars from either row of the market or take a towel from the market; towels cost 0, 1, or 2 sand dollars, with those dollars being placed in the same market row from which the towel was taken. When you place a towel, you must match at least one pattern with the towel that's rightmost on your beach board and you want to match as many patterns as possible. For each match you make, you advance that pattern's scoring marker 1-3 spaces on the score board; the closer to the ocean or the shade the more points you score, but if you place part of a towel outside the play area, you're penalized.
If you cover an umbrella, you receive its bonus, whether that's advancing a pattern's scoring marker or receiving one of two types of pearls.
When someone places a towel in the final column of their beach board, you complete the round, then see who's scored the most points from patterns, pearls, and leftover sand dollars, which are each worth a point. Instead of playing with umbrellas, you can flip your beach board to find a septet of sand crabs. Whenever you cover a crab with a towel, the crab crawls onto that portion of the towel, costing you both that pattern and a few points.