Would you believe three short lengths of PVC or ABS pipe (PVC is not always readily available in large enough diameters for your tripod legs) with end caps? Slip them over the legs of your tripod, et voilà, your tripod has better Wellies than you do.
The same trick works using longer pipe for using a tripod in water. And you can secure the pipe with elastic loops or slit the pipe (make one or two longitudinal cuts) and use something like a hose clamp -- how complex the setup gets is up to you. (You can even epoxy thumbscrews or knobs to the hose clamp's tightening bolt.)
EDIT: I should add that tripods like the Benbo, which have only two leg segments with the larger-diameter tube at the bottom, have this sort of protection built-in. I was rather spoiled by my Benbos. They're heavy and awkward to carry around without a dedicated, padded bag (the padding's for you, not the tripod -- the huge leg and center column lock knobs and the main bolt tightening lever are easy to use when it's cold enough to keep your nitrogen slushy cool, but that comes at a price), and they take a lot of getting used to, but you can't kill 'em with a bazooka. Or with a bucketful of microscopic bazookas. After a lot of excursions I'd pretty much need to rebuild my ball head, but the tripod(s) never needed more than a hosing-down and a quick spritz of WD40 (to get rid of the residual water in the main bent-bolt assembly-- the "WD" in the name stands for "water displacement"). I got rid of the Benbos when I got rid of everything else (turning pro ruined a hobby I loved, so I went "cold turkey" for more than a decade), but if I were physically capable of the hiking/scenic scene now, I wouldn't hesitate to get another Benbo.