In addition to @Itai's answer, I'd like to add, if you don't want to spend 1200$ on a tripod just to protect it from sands, you can use a little care, or on extreme situations, alternative DIY methods.

I also wrecked a tripod (not totally wrecked, but the sands kind of jammed the levers on the legs) by using it near a beach on a windy day. The next time I took some plastic (polythene) bags, cut them into long pieces (3" width) and adhesive tapes to put them around the leg lever joints like bandages. Worked like a charm. The only problem is, once you tape them in, you lose the ability to adjust the tripod height by extending the legs, otherwise this is good enough if you're not planning to go all out beach shooting. Adjust the tripod height before applying the tapes and you're good to go for that day.

And after the shooting, get to a safe place and use a rocket blower to blow off any accidental remaining sand particles near the lever joints just to be on the safe side.

DISCLAIMER: This method doesn't look pretty.

Additional Tips:

• Accept the fact that a tripod is a tool, it's OK if it gets dirty. Metal tripods will eventually corrode if you expose it to salt water on a regular basis. Get a carbon fiber tripod to prevent corrosion.
• Make it a practice to always extend the lowest section to keep the joints out of the sand.
• A broad sand "shoe" is useful in both sand and mud to keep the leg from sinking.
• If the tripod gets dirty, keep it extended until you can clean it.
• Any decent quality tripod will take many, many years to corrode to the point it really matters with occasional exposure to sand/salt water. So, open up all the legs, wash and rinse it thoroughly using clean water and wipe it dry before storing it.