🔍 Key Concepts

• Review how to use a nautical chart to find the charted depth beside a buoy in a dredged channel • Understand the meaning of "height of tide is negligible" in relation to charted soundings (soundings are usually referenced to mean lower low water – MLLW) • Consider the dredged channel controlling depth versus the natural bottom depth shown on the chart

💭 Think About

• Look up R “14” on the appropriate chart and note exactly where a vessel would be when it is "close abeam in your designated channel". What sounding or depth applies at that position? • Ask yourself: if tide height is negligible, should you be adjusting the charted depth up or down, or using it as-is? • Consider whether the depth you’re interested in is the depth in the center of the channel, at the edge of the channel, or directly under the buoy itself.

✅ Before You Answer

• Confirm the chart datum used for soundings on the chart (usually MLLW) and how that relates to "negligible" tide height • Verify the controlling depth or maintained project depth of Thimble Shoal Channel from the chart notes and dredged area markings, not just the single sounding near the buoy • Make sure you understand that a fathometer reads depth of water under the keel, not depth below chart datum, and relate that to the printed charted depth if vessel draft is ignored in the problem.