The nomenclature of the sea can be a vexing subject, not only for those who are new to it but also to those who are said to have saltwater in their veins. Even knowing what to call those “things” that sailors use to “go down to the sea” can be challenging.
One of the quickest ways to establish yourself as a naval novice is to refer to a ship as a boat. Unfortunately, there is no absolute way to define the difference. However, some criteria can be applied to help those who care to try.
In general, a boat is a watercraft (for want of a better word) that is small enough to be carried on board a larger one, and that larger one is a ship. This is sometimes expressed this way: “A ship can carry a boat, but a boat can never carry a ship.”
Also, if a vessel has a permanent crew with a commanding officer assigned, it is more than likely a ship. If a vessel is manned only part of the time (when it is in actual use), it is probably a boat. But this distinction runs into shoal water with such things as PT boats, which—despite the name—were organized and used much like ships.
Another distinction sometimes made is that a ship is designed to “navigate in deep waters,” but there are some pitfalls with this, too. The simplest rule that works most of the time is that if it is big, it is a ship. Don’t call a destroyer or a cruiser a boat.
Sometimes, when it is not clear whether we are dealing with a small ship or a big boat, the term “craft” is employed. For example, to fight in the brown and green waters of South Vietnam, there emerged a vessel that suffered from an identity crisis. Permanently manned by a crew led by an officer-in-charge, it was known officially as the PCF—which stood for patrol craft fast—but was more often called a “swift boat.” At least no one called them ships, as far as I know.
Now for some added confusion. Using the above guidance, submarines are technically ships. Yet they are traditionally referred to as boats. The original submarines were very small and manned only when in use, so “boat” was appropriate. But as they developed into larger vessels—and rightfully should have been called ships—the original term stuck. When the large nuclear subs began to appear, there was an attempt by some submariners to start calling them ships, but as with many things in the Navy, tradition trumped logic, and today, all submarines—even the giant “boomers” (fleet ballistic-missile submarines)—are called boats.
Another exception sometimes encountered is that personnel who are assigned to air wings that are embarked on board aircraft carriers will sometimes refer to the carrier as “the boat.” There is no official sanction for this, but it seems to be a kind of affectionate irreverence they use to set themselves apart from their fellow sailors who are assigned to the carrier as a part of her permanent crew (or they are merely uninformed aviators!). Having served in two of these magnificent monsters, I have no doubt that an aircraft carrier is a ship—let others call it a boat if they must.
Another term that causes some consternation in naval circles is the word “vessel.” Some cantankerous, would-be purists insist that a vessel is “something used to carry water, not to go to sea in.” But the Dictionary of Naval Terms (Naval Institute Press, 2005) defines “vessel” as “every description of craft, ship, or other contrivance used as a means of transportation on water.” Other dictionaries confirm the acceptability of this term, including Webster’s—“a watercraft bigger than a rowboat.” Perhaps most convincing of all is that “The Official Inventory of U.S. Naval Ships and Service Craft” is formally known as the “Naval Vessel Register.” So, the bottom line is that vessel is an acceptable term in most naval circles.
One last comment regarding ship references. Tradition has long mandated the use of feminine pronouns when referring to ships, as in, “She has a new sonar, making her a good ASW ship.” This practice may be a dying one (Lloyds of London, the longstanding British maritime insurance company, no longer uses the feminine), and you will no longer be “keelhauled” for not using it, but you will still frequently encounter the practice—including in the pages of Naval History—and partaking is largely a function of the adage, “Know your audience.”
All of this nomenclature is further complicated when we introduce more specialized terms such as “cruiser” and “destroyer,” as well as other variations such as frigate, corvette, brig, and battleship. But that is a discussion for another time.
Lieutenant Commander Cutler, a former gunner’s mate second class, is the Gordon England Chair of Professional Naval Literature at the U.S. Naval Institute. His many books include numerous editions of The Bluejacket’s Manual (Naval Institute Press), a copy of which every U.S. Navy enlistee receives.