The rise and fall of the tides play an important role in the natural world and can have a marked effect on maritime-related activities. Here, a ship's crew inspects the hull of their vessel. It became stranded on a sandbar following a rapidly receding tide.

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Maritime activities throughout the world depend on accurate tidal and current information for safe operation. NOAA's National Ocean Service collects, studies and provides access to thousands of historical and real-time observations as well as predictions of water levels, coastal currents and other data.

The Tides and Waters Levels Tutorial is an overview of the complex systems that govern the
movement of tides and water levels.

The Roadmap to Resources complements the information in the tutorial by directing you to additional information and data from NOAA and other reliable resources.