Beach Volley level 6-12 is a bit difficult, but only relies on one shot. Our strategy is to fire the Red birds a little above horizontal, looking for the right angle to topple the main structure. It is not very stable, so only one or two hits are needed. The score in the video below is 97,200.
Note: The first Red bird in this level has been replaced with a Yellow bird. While the strategy remains the same, you can now speed a Yellow bird over the umbrellas into the structure beyond. Since the level is now easier to complete, the video below will suffice.