A new reader recently asked why “ships” he saw on the sixth boro showed up on AIS as tugs. An excellent question, and not the first time I’ve heard it. . . . Read the first sentence of the wikipedia definition of “ship.” By that definition, how many ships do you see here? (Doubleclick enlarges most.)
Answer is only one, the orange one. The nearer vessel is a barge. The major difference is that a barge lacks its own means of propulsion: no engine, props, or sails. Barges get moved by a tugboat that may tow, push, or strap-on alongside aka on the wire, in push gear, or on the hip, respectively.
Answer is . . . one, Maersk Elizabeth.
Answer is . . . none. Some “tugboats” lack the equipment to tow; they have no winch. Instead, tugs like Laurie Ann Reinauer connect by the bow into a notch designed in the after portion of the barge. Massive pins then lock into structures on the barge inside the notch.
One ship, Princimar Strength, also shown below with two barges and two tugs alongside.
And finally . . . no ships here, just two barges (Energy 13502 and Charleston) with a tug Eagle Service in between.
All fotos by Will Van Dorp, who could use a bit of help with complexity.