For a canal to qualify as a ship canal, it must have a minimum depth of at least 5 metres (16.4 feet), although many are much deeper. The purpose of a ship canal is:

1. To create a shortcut and avoid lengthy detours.
2. To create a navigable shipping link between two land-locked seas or lakes.
3. To provide inland cities with a direct shipping link to the sea.
4. To provide an economical alternative to other options.

List of important ship canals (by length):

Navigability

The standard used in the European Union for classifying the navigability of inland waterways is the European Agreement on Main Inland Waterways of International Importance (AGN) of 1996, adopted by The Inland Transport Committee of the United Nations Economic Commission for Europe (ECE), which defines the following classes. (This table is incomplete.)