Sandless beach blankets are still under development, but there are some options for those who want to enjoy their day at the beach but not bring home too much of it.
Quite simply, the idea of a sandless beach blanket is that it will not absorb or hold any sand, so that when you are packing up to go home, you can stow it away without feeling like you've brought back half the beach with you.
The Sand Free Beach Sheet claims to be exactly what you want; sand does not stick to the surface and there is no need to shake it out, although, keep in mind, that these are not true sandless beach blankets.
The Neat Sheet Ground Cover, talked about at Ask the Plant Lady, is considered a sand-resistant, rather than a sandless blanket.