You are underway in a vessel with a draft of 7.0 feet (2.1 meters). The charted depth for your position is 9 fathoms. You compute the height of tide to be +3.0 feet (0.9 meters). You determine the depth of the water beneath your keel to be __________.
• Soundings on charts are usually given in fathoms or feet — know which unit is used here • Tidal height is added to the charted depth to find the actual water depth at the time • To find under-keel clearance, subtract the vessel’s draft from the actual water depth
• First convert the charted depth from fathoms to feet, then adjust it using the computed height of tide — what is the total depth of water at that moment? • Once you know the total depth of water, how do you use the vessel’s 7.0-foot draft to find the clearance under the keel? • Check whether each answer choice could reasonably come from your calculated total depth minus the draft
• Confirm the fathoms-to-feet conversion (how many feet are in one fathom?). • Be sure you are adding the height of tide to the charted depth, not subtracting it. • After finding the total water depth, subtract the vessel’s draft and compare the result to the answer choices.
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