i use a manfrotto and rinse it in the shower while still at the beach to prevent the clamps from seizing up. later, i soak it in the bathtub or disassemble it and do a thorough cleaning. spray locks with WD-40 to remove the water and all set for next time.
some tips, for sand shooting, lower the smallest segment of the leg first (contrary to usual tripod theory), to keep the lowest clamp from being submerged...this keeps the sand out in the first place. Also, spread legs as wide as they will go and really jam the legs into the wet sand as the wave is in. If you have a center column, this is what it was made for, a 4th leg in wet sand.