Canal locks in the context of "McAlpine Locks and Dam"

A body of water, such as a river, canal or lake, is navigable if it is deep, wide and calm enough for a water vessel (e.g. boats) to pass safely. Navigability is also referred to in the broader context of a body of water having sufficient under keel clearance for a vessel.

Such a navigable water is called a waterway, and is preferably with few obstructions against direct traverse that need avoiding, such as rocks, reefs or trees. Bridges built over waterways must have sufficient clearance. High flow speed may make a channel unnavigable due to risk of ship collisions. Waters may be unnavigable because of ice, particularly in winter or high-latitude regions. Navigability also depends on context: a small river may be navigable by smaller craft such as a motorboat or a kayak, but unnavigable by a larger freighter or cruise ship. Shallow rivers may be made navigable by the installation of locks that regulate flow and increase upstream water level, or by dredging that deepens parts of the stream bed.

The Canal of the Pharaohs, also called the Ancient Suez Canal or Necho's Canal or Darius Canal, is the forerunner of the Suez Canal, constructed in ancient times and kept in use, with intermissions, until being closed in 767 AD for strategic reasons during a rebellion. It followed a different course from its modern counterpart, by linking the Nile to the Red Sea via the Wadi Tumilat. Work began under the pharaohs. According to Darius the Great's Suez Inscriptions and Herodotus, the first opening of the canal was under Persian king Darius the Great, but later ancient authors like Aristotle, Strabo, and Pliny the Elder claim that he failed to complete the work. Another possibility is that it was finished in the Ptolemaic period under Ptolemy II, when engineers solved the problem of overcoming the difference in height through canal locks.