Let's face it, watering the house batteries in any boat is a pain in the
ass. Dragging out all the stuff on top of the battery boxes....crawling
around inside awful compartments full of engines, water heaters and much
nastier crap to peer down inside that very back cell you wished you'd never
put where it is.....we've all been there, done that, cursed and hurted.

I found this gadget from an ad in homepower.com magazine:
http://tinyurl.com/nmo2z

part of http://janwp.com/

Water all the batteries at once with valves to level each cell just right.
What a cool idea.....