At roughly 16 feet long, the Dozer Boat (steel pushboat; aka: Barrier Boat) is the smallest active-duty vessel in the U.S. Navy fleet.
Originally built for the logging industry to push 30,000 pound logs down rivers in the Pacific North West, most Naval Barrier Boats were destined for hard lives pushing logs.
Now, they typically push out large boats and submarines.
A vessel like that is considered support craft. It would not be commissioned like a regular Navy ship or Coast Guard cutter. The sailors that operate them are usually craftmasters, which carries its own badge.
They are built with a durable 1/4 inch steel hull out front increasing to 3/4 inch thickness in key areas.
In the engine room of these mini-tugs is a North Carolina- built Cummins QSM 11 diesel engine, a 10.7L turbocharged inline 6-cylinder, good enough for around 400 HP and 1,800 lb-ft of torque. That’s more torque than any supercar sold today. With an operating RPM of around 1,800 RPM, these tugs have all the low-end grunt to push boats and submarines hundreds of times its weight.