Shore port crane for Cargo Ships. Hover the crane and press R to toggle mode: loading or unloading. Requires straight-waterway directly in front (3x3) and within 2 tiles of shore.
I currently have straight waterway as close to a straight area of land as possible and I still can't place a crane even if I have a cargo ship on the waterway
Or maybe it's invisible because I do have some weird looking blue boxes on the areas where I tried to place them
