I like the idea for freshwater on the boat. That would be nice to get the salt off me at the end of the day. I may try to plumb in a quick connect water tank for the bow tied into the washdown pump with a tee and valve. Good idea
and also the future conduit idea, plenty of room under the tank.
Looking down my gunnels, I only have around 2" of clearance between the cap and hull above the bulkheads until you get about half way up. Any 3" conduit would have to go through my stringer and through 3 of those bulkheads, I really really want to avoid cutting into all of that since I already have to cut the stringer for the fuel fill and vent.
Here is a pic looking between the cap and hull inside the gunnel