🔍 Key Concepts

• Tidal datums such as mean high water (MHW), mean lower low water (MLLW), and their typical chart uses • How shorelines and charted depths are referenced to different vertical datums • Differences between datums used for sounding depths and those used for coastlines/contours

💭 Think About

• Ask yourself: Is mean high water normally used for charted depths (soundings), or for defining where the land ends and the water begins on charts? • Consider which U.S. coasts or waters use mean lower low water versus other datums for soundings—does MHW fit that role? • Think about what bottom contour lines represent on a chart and whether they are drawn relative to high water, low water, or another datum.

✅ Before You Answer

• Identify which datum (e.g., MLLW vs MHW) is standard for sounding depths on most U.S. nautical charts • Determine which datum is commonly used to depict the shoreline on charts in tidal areas • Check whether any answer choice is actually describing mean lower low water or another datum rather than mean high water