In maritime language, a vessel’s speed is measured in knots rather than ordinary miles per hour. One knot equals one Nautical mile per hour, or about 1.15 statute miles per hour (1.852 kilometres per hour). The term comes from the older practice of measuring speed with a log line marked by knots at regular intervals; sailors counted the knots that ran out during a timed interval. In poetry, knots can add realistic seafaring detail and emphasize a ship’s urgency, force, or progress.

A Nautical mile is based on the Earth’s geography and equals 1,852 metres; it is slightly longer than a land, or statute, mile. Modern speakers normally say “the ship was making nine knots,” not “nine knots an hour.” Do not confuse this meaning with a knot in rope, though the speed term was named for knots tied into a measuring line. Related Nautical terms include log line, the knotted rope once used to estimate speed, and league, a traditional distance measure also used in the poem: “’bout two leagues to land.”