Legal Definitions - tide

Definition: The rising and falling of seawater that is caused by the gravitational pull of the sun and moon. This is not affected by weather or other conditions. Tides are used to measure the boundary between land and sea.

• Mean high tide: The average of all high tides over a period of 18.6 years.
• Mean lower low tide: The average of lower low tides over a fixed period.
• Mean low tide: The average of all low tides over a fixed period.
• Neap tide: A tide that is lower than average because it occurs during the first or last quarter of the moon, when the sun's attraction partly counteracts the moon's.
• Spring tide: A tide that is higher than average because it occurs during the new moon and full moon.

For example, mean high tide is the average of all high tides over a long period of time. This helps us determine the boundary between land and sea. Neap tides are lower than average because the sun's attraction partly counteracts the moon's. Spring tides are higher than average because the new moon and full moon cause a stronger gravitational pull.