This is looking into the area under the dinette seating. (forward) The stock holding tank was located here. That blue thing you see, replaces the holding tank. It's the LectraSan.
The bronze Tee splits one through hull so as to provide the head with water (to the left) and water for the anchor wash pump. It's hidden at the top of the screen. That fitting to the left of the tee is a check valve. (clapper style) It prevents the wash pump from drawing water from the head hose. That way the head stays primed. Most of the rest of the plastic piping and black hose is for the water heater that is just inboard of the LectraSan. That black thing to the right, is the passive radiator for the sub woofer. Note the gasket material around the hatch opening. It keeps the hatch lid from vibrating because of the sub woofer. The wiring is for the sub too.