shoal

Imagine sailing along and suddenly the water becomes much shallower. You may be near a shoal. A shoal is a shallow area of water, often made of sand or rocks, and it can be dangerous for boats. The word is also used for a group of fish swimming together, as in "a shoal of herring." In older or literary English, it can also mean a large number of people or things. So when you hear "shoal," think of shallow water first, but sometimes fish or a packed group.

The word "shoal" moves through English with a strong connection to the sea. Most often, it refers to a shallow area of water, sometimes a sandbank or rocky stretch, where the depth drops enough to create a danger for boats and ships. Sailors do not want to run aground on a shoal, because what looks like open water may suddenly become too shallow to pass safely.

The word also refers to a group of fish swimming together. You might read about a shoal of sardines or herring moving in the same direction through the water. In everyday English, people often say "school of fish," but "shoal" is also a standard and well-known choice, especially in natural description and general writing.

There is also a broader and less common meaning: a shoal can mean a large number of people or things gathered together. This sense now feels older or more literary than the water-related meanings, but you may still come across it in descriptive writing.

So the word carries two main ideas: shallow water and fish moving together, with an older extra sense of a large number. Whether you meet it on a nautical chart, in a nature book, or in a more literary passage, it suggests either a risky shallow stretch or a gathered mass moving as one.