Fuel: 20 gallon cylindrical stainless steel tank located in the starboard cockpit locker. It is held down to tabbed in bulkheads with stainless steel strapping with a rubber pad for cushioning. It looks easy to remove but I have measured and I would need to take the teak lip off the opening to the cockpit locker. It's close so I'm not sure if that would be enough or if I'd need to cut into the fiberglass to get it out once the teak was removed.
Water: Glass integral tank under the V berth. It ain't coming out but has a good access port for cleaning and is in good shape after 36 years.
Holding: It was in the cabinet behind the head but it started to leak and I couldn't find a drop in replacement. I relocated it under the V berth just forward of the head with a slightly larger tank. The guy that did the install for me was, um, not very professional. He managed to get it installed and it is now held in place with a thousand #10 screws holding a plywood cover pressing down on foam to clamp it in place. I would need to remove the thousand screws to get at the access port but I really don't have any desire to go in there anyway.