I know it isn't possible for most but if you do have it on board, a hydraulic high pressure wash down pump is pretty small and with 4000 psi (adjustable) you can cut kelp off the anchor, never mind clean off mud. In fact, it is my favorite piece of equipment on the boat because it saves so much time for general cleaning. Mine uses fresh water because we carry a fair amount, but I don't see why you couldn't use filtered sea water if you rinsed it with fresh.
"Dad always thought laughter was the best medicine, which I guess is why several of us died of tuberculosis." - Jack Handy