Southampton has a famous “double tide” with each tide rising for up to 7 hours, followed by an ebb tide of less than 4 hours. This provides Southampton with up to 17 hours of rising water every day, which is ideal for the shipping industry.

A “young flood stand” of some two hours occurs when the tide rises at mean tide level, with high water being maintained for a considerable period. Fortuitously for Southampton, it has two tidal waves which reach the shore after being channelled east through the Needles and west through Spithead. In addition, the central location of Southampton on the south coast gives it a lower mean tidal range than other ports such as Bristol or Lowestoft.

The “double tide” has been put to good use throughout Southampton’s history. Southampton Castle built its “garderobes” or latrines in the 14th century on the west shore, so waste could be swept away by the tide (with a second tide giving the garderobes a nice flush!). During the Second World War Southampton was Britain’s Number One Military Port, and the long hours of high water meant that more troops could board vessels over a shorter period of time than at other ports, which was of particular importance during the D-Day landings (more than 53,000 men and 7000 vehicles were to leave Southampton on D-Day).