Below is the unit of length for sea or nautical miles, as well as information about fathoms, cable length, and knots.
A fathom is 6 feet, the length of rope a man can extend from open arm to open arm. The rope was lowered into the sea to measure depth.
A cable length is the length of a ship's cable, about 600 feet.
A nautical mile is 10 cable lengths, or 6,076 feet.
1 nautical mile = 1.1508 miles
A knot is the measure of speed on water. One knot is 1 nautical mile per hour.