Apparently when I was a lad we were being given the “sea mile” measurement, we were definitely told 6,000 feet which is 1000 fathoms.
“The sea mile has also been defined as 6,000 feet or 1,000 fathoms, for example in Dresner’s Units of Measurement. Dresner includes a remark to the effect that this must not be confused with the nautical mile. Richard Norwood in The Seamans Practice (1637) determined that 1/60th of a degree of any great circle on Earth’s surface was 6,120 feet (vs the modern value of 6,080 feet). He added: “if any man think it more safe and convenient in Sea-reckonings” he may assign 6,000 feet to a mile, relying on context to determine the type of mile.[10][11]”
I guess you do know what a nautical mile is, at that.