Watch your boat's trim!
My '83 H25 has a flexible water tank centered under the cockpit. There is an access hatch cut in the side of the fiberglass shelf to get to it. I assume it was a factory installation. This arrangement puts the tank close to the sink, but you practically have to stand on your head inside the locker to reach the filler! I agree with MABell-- I'm going to remove the old tank from the cockpit & put a flexible bladder under the vee-berth in order to trim my boat out better. I have a 100 lb Honda 9.9 outboard hanging off the transom, and even with no people or gear on board, she squats too far down on her stern. I moved her three batteries (two under the port settee, one under the starboard), toolset, hellkits, etc., as far forward of her waist as possible but 'twarnt enough. I either need a central AC or water tank under the vee berth to balance her out.