This may or may not actually be more secure than putting your stuff in your shoes and piling a damp towel over them, but it may be worth it for avid beachgoers:
[Beach Vault] (Viewer #272,483)
The Beach Vault Kickstarter project:
Lay down! Close your eyes! Take a nap and let the sun kiss your skin with a beautiful shade … oh wait you can’t. The moment you arrived at the beach your friends and family went off to play volleyball, go surfing or take that all relaxing walk down the beach. You’ve been waiting for this moment to relax, you just want to shut your eyes, pop in your headphones and drift away, but that’s not possible. Why? Well, you’re currently guarding beach bags containing keys, wallets, cellphones, perhaps a kindle for reading or an Ipad. Well my friend, you don’t have to wait for someone to relieve you from your security post in order to begin relaxing. Let the beach vault do that for you!