Use the WEAK HAMMER on the device (A); take the ACID (B).
Return to the Fish Gates.
Use the ACID on the cage; take the SEA KEY (C).
Return to Marlenaâ€™s Tank.
Open the lock and use the SEA KEY in it (green); turn the valve: Rx2, L, R, and L.
Talk to Marlena to receive the BONE HEAD.
Return to Fabianoâ€™s Stage.
Place the BONE HEAD on the skeleton.
Set the joints as shown in the screenshot (D).
Take the BUTTON and CLOSET KEY (E).
Use the CLOSET KEY in the lock (F); turn it to activate a HOP.