A more thorough explanation:

Definition: A watergage is a structure built to protect against the force of waves and tides. It can also refer to an instrument used to measure the level of water.

Examples:

• A seawall built along the coast to prevent erosion and flooding is an example of a watergage.
• A device used to measure the depth of a river or lake is also called a watergage.

The first example illustrates the use of watergage as a seawall, which is a common application of this structure. The second example shows how watergage can also refer to an instrument used to measure water levels, which is important for monitoring water resources and predicting floods.