https://maritime-mile.com/profile/caisson-gate/
The Caisson Gate is the original Hamilton Dock gate and sits at the other end of the Hamilton Dock to the SS Nomadic. Built in 1867, the Caisson gate is one of the oldest remaining Harland & Wolff constructions, and is actually a vessel, given the hull number 50 in H&W’s shipping register. A hollow vessel built from wood and steel, the Caisson was a watertight entrance gate that allowed the dock to be emptied.
