The holding tank is under th v-berth. I know this because that's where the hose ends. I can't actually see the tank as it is inside a compartment that is glassed to the hull and covered with plywood that is also glassed to the hull. I am curious how the PO knew whan it was time to pump it out.......assuming he used the head of course. This would require surgery to remove.

The fresh water tank is under the starboard settee and although there is a panel that unscrews, that panel has no purpose. the tank would never fit through the hole, like the holding tank the compartment is glassed together and to the hull. Would need surgery.

The fuel tank is under the cockpit sole and is visible throught the port locker. I think it could be removed and replaced, although it would take a fairly small person to get in there.