MLLW is mean low low water. It's the average of the lowest tide each day at that location.
That's the standard used on nautical charts and also used for tide charts for the depth of the tides each day.
That's the standard used on nautical charts and also used for tide charts for the depth of the tides each day.
Many other countries such as Canada use Lowest Astronomical Tide. The difference is actually important to know at times when boating between the countries.
See https://en.wikipedia.org/wiki/Chart_datum#Choice_of_tidal_ph...