Difference between “float”, “swim”, and “sail” in English

by Jakub Marian

Tip: See my list of the Most Common Mistakes in English. It will teach you how to avoid mis­takes with com­mas, pre­pos­i­tions, ir­reg­u­lar verbs, and much more.

Non-native speakers of English sometimes incorrectly say that a non-living thing, such as a boat or a piece of wood, “swims in the water” because that’s the way they would say it in their native language.

In English, however, only a living thing (such as a person or an animal) can swim, because swimming is an intentional activity, not something that is being done to a person or a thing (but there are a few exceptions mentioned at the end of the article). When a non-living thing moves in a river simply because it is being carried by the stream, the correct verb to use is float:

correct There was a big log floating in the river.
unnatural There was big log swimming in the river.

Living things can also float when they don’t intentionally move and don’t sink, as in

He was tired of swimming, so he just lay on his back and floated in the water.

(note that “lay” is the past tense of “lie” here). But what when you speak about a ship or a boat? Ships typically do not just float; they are operated by humans in order to move from one place to another. The correct verb to use in connection with a boat or a ship is sail (but using a generic verb like “go” or “travel” is fine too, of course):

correct The ship sailed from Hamburg to New York.
wrong The ship swam from Hamburg to New York.

It may seem strange to use the verb “sail” to speak about ships that have modern engines and propellers, but that’s just the way the verb has been used since the times when all ships had sails.

But what about submarines? Submarines never had sails (even in the past), but it turns out that the same verb was also extended to them:

correct The submarine sailed to Pearl Harbor.
wrong The submarine swam to Pearl Harbor.

Another, somewhat less common verb used in connection with submarines is “cruise” (e.g. “the submarine cruised to Pearl Harbor”).


When I wrote that “only a living thing can swim”, it was not the whole truth. When referring to robots (both autonomous and remote controlled) that can move in water, it is commonly said that they swim, even though they are not living beings in the traditional sense of the word.

The verb “swim” can also be used figuratively to express that something is covered with a large amount of liquid, e.g.

The main course was swimming in oil.

It can also be used to describe things moving around you, especially when you feel dizzy, for example,

After finishing his sixth beer, the room seemed to swim before his eyes.

By the way, if you haven’t read my guide on how to avoid the most common mistakes in English, make sure to check it out; it deals with similar topics.