how 2 measure in older days by using the way, fathom?

Answer 1

A fathom is 6 feet

one would stand on the front of the vessel and throw a weighted rope that was knotted every 6 feet - when the rope hit bottom -
it would be pulled up hand and counting the knots you passed - you could tell how many fathoms were below you

Answer 2

oh in the old days...i feel old.

the way you measured a fathom was by the length of rope that when held by two outstreched arms and hands from the body, averaged six feet. this was the rapid way to measere the depth when any rope was thrown over the side.