🔍 Key Concepts

• Tidal datums used on nautical charts • Difference between mean low water and a single low tide event • How averages are calculated over a long period (e.g., 19 years)

💭 Think About

• Is mean low water based on just one of the daily lows, or on more than one kind of low tide over time? • Does mean low water refer to a single tide occurrence, or to a statistical average used as a chart reference level? • Which choice best matches a long-term average of low tides only, rather than including highs?

✅ Before You Answer

• Make sure the option you choose refers only to low waters, not highs and lows mixed together • Check that the definition implies an average over many days/years, not a single day’s tide • Confirm that the wording matches a datum used for chart depths, not simply a description of the ocean surface