Ah, now here's a subject I've brought up before on AP and a handy little accessory I now use.
Firstly, any water or sand is easy to wash off afterwards anyway so dont be concerned, I immersed my Velbon Tripod many times in sea water etc, and a quick rinse off fixes it.....but
One problem I have found is using my tripod on soft surfaces like mud or sand is finding the legs sinking and never being quite stable enough. I have often thought camera accessory manufacturers could do well to make a cheap basic snap on/push on wide plate foot for a tripod to minimise sinking as the weight is spread out more evenly, rather than a small pressure point as tripods have now. I was wandering through one of the discount stores the other day and came across these for $1.00 for a bag of gazebo fittings. They fit onto most tripod feet nicely and work a treat, I reckon something similar could be found in places like Clark Rubber or elsewhere