Accompanying text: "Powerfull new U.S. Tug at work. A new U.S. tug, most powerful of its size and known as the Ingalls Sea Mule, tows a heavily-laden barge during trials in a U.S. port. Easiliy handled by a crew of five, the Sea Mule can either tow or push barges in harbour operations. Forty-two feet (12.6) long, and 15 feet (4.5 meters)broad, this tug develops 500 horsepower, and can travel 10 miles (16kilometers) an hour. The Sea Mule can be tranported in sections on railway cars and ocean-going ships, and can be asembled in a few hours".

More info (from https://www.rcgroups.com/forums/showthread.php?3506927-WWII-USN-Sea-Mule-Tug). Rather than building a traditional boat, the Sea Mule was really four pontoons bolted together to form a motorised barge.The two stern pontoons each housed a Chrysler Royal Marine Straight 6 (M8) petrol engine, and the two forward pontoons each held a fuel tank of about 700 gallons. No pilot house, or any kind of protection, was provided. A basic console for the wheel and throttles was on the deck, with a rudimentary safety rail.

The Sea Mule was a 41ft long and 14ft wide. Not at all good looking, but perfect for its role – robust, effective, cheap and simple to use. They could easily be transported in their crates or assembled, by road, rail or as deck cargo.

The pre-fabricated mini tug came in 4 crates and could be assembled by its crew of 3 in a couple of days, using only the tools included, and a gas welding set. Assembly was very simple and could be handled with a very basic level of skill and equipment. The assembly instructions are only 42 pages and much easier to follow than anything from Ikea.

The tug components were built by Chrysler in Detroit, and Ingalls Iron Works in Birmingham, Alabama, to a pretty standard Bureau of Shipping template. The engines all came from Chrysler.

Here's a link to a video showing one in action: https://www.criticalpast.com/video/65675077930_sea-mule-tug_pulling-a-vessel_ships-underway_men-aboard-a-tug