A bulk material unloader includes parallel, spaced-apart main and back barges or pontoons which are held in fixed relationship with respect to each other by four collar frames. Two parallel cargo lighters are positioned between pontoons and the unloader is moored alongside ship. The two midship collar frames support a two-legged main tower over the main barge and a two-legged back tower over the back barge. A horizontal boom assembly includes a back bridge extending between the towers and an outboard boom supported by the towers and normally extending away from the back bridge and over the ship in parallel, end-to-end alignment with the back bridge. A horizontal bulk material conveyor assembly on the horizontal boom assembly includes two fixed parallel top horizontal endless belt-type conveyors supported on the back bridge and two parallel bottom horizontal endless belt-type conveyors supported on the boom assembly to move back and forth under the top conveyors and situated to receive bulk materials leaving the top conveyors. A chute is mounted at the outboard ends of the bottom conveyors, and bulk material deposited on the bottom conveyors is discharged into the chute for delivery to a hold of the ship. A bucket trolley and a grab bucket run on tracks which extend the entire length of the boom assembly. A hopper is situated on the back barge under the tracks so the bucket can deposit materials from the lighters into the hopper. An elevating conveyor carries materials from the hopper to the top horizontal conveyors. The chute is removable for offloading so the bucket trolley can move out to the outboard end of the outboard boom.