🔍 Key Concepts

• Charted shoreline / coastlines and what water level they are referenced to • The meaning of mean high water, mean low water, mean lower low water in tidal terminology • Why charts in areas with large tidal ranges need a consistent tidal datum (reference level)

💭 Think About

• Ask yourself: When you stand on a beach with a big tidal range, which water line best represents the average place where the sea regularly reaches the land? • Think about which tidal datum is normally used as the vertical reference for soundings (depths) versus which is used for shorelines on most charts. • Consider why using the lowest regular tide line for the shoreline might be misleading to mariners planning coastal navigation or beach landings.

✅ Before You Answer

• Review the definitions of mean high water (MHW), mean low water (MLW), and mean lower low water (MLLW) in a tides/tidal datums section of your study materials. • Confirm which tidal datum is normally used for chart soundings versus which is used for shorelines and coastal boundaries. • Make sure the option you pick is a specific tidal datum, not a vague or non-standard term.