What is a meter?
The meter is the SI base unit of length and is equal to 100 centimeters or 1,000 millimeters. It was originally defined as one ten-millionth of the distance from the North Pole to the equator along the meridian through Paris. Since 1983 it has been the distance light travels in a vacuum in 1/299,792,458 of a second.
What is a UK nautical league?
A UK nautical league is three UK nautical miles, ie 18,240 feet or 5,559.552 meters, which rounds to 5.56 kilometers. The international nautical league is slightly shorter at 5,556 meters.
Don't confuse it with the land league, which is three statute miles. The nautical league is three nautical miles, about 3.45 statute miles, so it's roughly 15% longer.
Britain's territorial waters once reached one marine league – three nautical miles – from the coast. The limit has been 12 nautical miles, or four leagues, since 1987.