Incase your rail in a giant bubble ... it can be liek one of those giant water balls at the lake or in the pool lol you drive and it rolls... muahahaaa
Id say the bag trick with maybe some 3m clear tape on the lens glass ... kinda like the clear plastic cover that comes on pda phones or a tv when you 1st buy it...
or the best way would be to buy a camera that was intended for the sand
Capt