Tie barges together into tow units for tugboats to handle, inspecting barges periodically during voyages and disconnecting them when destinations are reached. Attach hoses and operate pumps to transfer substances to and from liquid cargo tanks. Handle lines to moor vessels to wharfs, to tie up vessels to other vessels, or to rig towing lines. Read pressure and temperature gauges or displays and record data in engineering logs. Stand watch in ships' bows or bridge wings to look for obstructions in a ship's path or to locate navigational aids, such as buoys or lighthouses. Maintain government-issued certifications, as required. Examine machinery to verify specified pressures or lubricant flows. Maintain a ship's engines under the direction of the ship's engineering officers. Break out, rig, and stow cargo-handling gear, stationary rigging, or running gear. Lubricate machinery, equipment, or engine parts such as gears, shafts, or bearings. Lower and man lifeboats when emergencies occur. Sweep, mop, and wash down decks to remove oil, dirt, and debris, using brooms, mops, brushes, and hoses. Splice and repair ropes, wire cables, or cordage, using marlinespikes, wire cutters, twine, and hand tools. Load or unload materials, vehicles, or passengers from vessels.