Seamanship

Size Matters

What is the difference between a ship and a boat? It’s one of the questions I am most frequently asked. One would imagine that after several thousand years of seafaring, we’d have a simple and concise answer.

We don’t. Most of the answers I’ve heard are somewhat true some of the time, but never true all of the time.

Ships sometimes ride on larger ships; boats sometimes carry smaller boats. Some boats have multiple decks. Some ships lack permanent captains or crew, while some boats have both. And, like ships, larger multihull boats don’t heel much when they turn. Add to this the variety of new hull types that do not conform well (or at all) to traditional ship design, and the challenge of answering the question seems even more daunting.

The fact that military, commercial and recreational vessels all use different tonnage conventions doesn’t make the task any easier, but those differences are not as problematic for this purpose as one might expect. In trying to ascertain

the magic size beyond which a boat is unambiguously a ship, it’s useful to look at where a variety of sources—commercial and military—converge.

The smallest class of military vessels universally considered ships is destroyer escorts. The next smallest military vessels (corvettes and patrol boats) are unambiguously called boats. Pictured on the next page is the USS Buckley, DE-51, the lead ship of the most prevalent U.S. destroyer escort class of World War II. The Buckleys were 306 feet long with a displacement of 1,673 long tons. Those specs are a good benchmark, as the Buckleys are the smallest U.S. naval vessels to be considered ships.

Next, consider the realm of U.S. Coast Guard licensing for the U.S. Merchant Marine. The licensing categories are based on gross register tonnage (GRT). A register ton is a measurement of volume: 100 cubic feet. GRT is the total volume of all the permanently enclosed spaces on a vessel.

The Coast Guard categories for small boats, large boats