Tidal Ranges increase and decrease twice every 28 days, as the moon waxes and wanes.

• Full Moon - Spring Tides
• First Quarter - Neap Tides
• New Moon - Spring Tides
• Third Quarter - Neap Tides

When planning dives in strong tidal areas for 2009 & 2010, it is best to choose dates around neap tides. The reduced tidal flow around neap tides usually results in improved water visibility and increased "Slack Water" times.

These graphs are provided as an aid to dive planning. It is the responsibility of the dive manager to obtain correct tide and weather information for any site you wish to dive.

The following tidal curves have been produced using tidal data for Cardiff, but 2009 & 2010 Spring and Neap tide dates will be consistent throughout the UK.

For the purpose of regularity across these charts, certain dates in each month are repeated. Weekend dates are highlighted in yellow.

Graphs for 2011 spring and neap tides will be added later next year.