If a chart indicates the depth of water to be 6 fathoms and your draft is 6.0 feet, what is the depth of the water under your keel? (Assume the actual depth and charted depth to be the same)

Correct Answer: Option C — 30.0 feet

Convert fathoms to feet by multiplying 6 fathoms by 6 feet per fathom, yielding 36.0 feet of charted depth. Subtracting your 6.0-foot draft leaves a net clearance, or depth under the keel, of exactly 30.0 feet.