Complex sentence: Viking soldiers also used this instrument in a similar fashion, using a lead weight, they measured the length of the rope when they hauled in on board in fathoms, this unit of measure is still used today for nautical depths.
Split into simpler sentences: Viking soldiers also used this instrument in a similar fashion. Using a lead weight, they measured the length of the rope when they hauled in on board in fathoms, the unit of measure still used today for nautical depths.