Lots of mud comes up packed in the chain links. A deck wash is almost essential, I'm not sure how you would keep mud out of the bilge otherwise. That was another one of those upgrades which was much easier than I had imagined.
My two 24 gallon water tanks are tucked into the bilge over the keel. An advantage of a full fixed keel vs a centerboard, I suppose. I have fitted a holding tank in the space under the vee-berth. There is some space underneath allowing me to pull the surplus chain aft to help trim the boat.