The Tidal Diamonds are the symbols marked usually on British Admiralty Charts that indicates the direction and speed of the Tidal Streams at particular location. The Tidal streams are given in the form of the table and tidal diamonds are marked in the first row. The Tidal diamonds are marked by purple color rhombus and contains Alphabetical letter starting from A, B, C and so on... The Tidal diamonds accompanies the position (mentioned in Latitude and Longitude) next to it and refers to the position on the chart on which the calculated tidal stream is expected.