Final answer:
If sailors recorded the depth of water at S fathoms, the depth of the water in feet would be 6S feet since one fathom equals six feet.
Step-by-step explanation:
When sailors measured the depth of water using a unit of measurement known as a fathom, they were effectively measuring in units of six feet. One fathom equals six feet. Therefore, if they recorded the depth of water at S fathoms, the depth of the water in feet would be 6S feet.
Historically, sailors measured depths by using a rope with knots tied at every six feet, letting it drop over the side of the ship until it hit the bottom. To calculate the depth, they simply counted the knots. Now, modern techniques like sonar are used to determine the depth with greater precision.
The correct answer to the question, therefore, is option a) 6S feet.