Sea Swimming Conditions
By Paul Smith
Contents
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Tides
Currents
Wind
Weather
Tides
•Each 25 hour period is divided up into 4 tides
(approx 6.25 hours apart).
•There are 2 high and 2 low tides within this
period.
•At low tide the sea retreats and usually sand will
appear.
•At high tide the sea will reach its furthest point
up the beach (often marked by dried seaweed
and small pieces of driftwood).
Tide Tables
Tables showing the tide times and the height of the
tides can be picked up at surf shops, the marina and
online (there is even an iphone app!).
Tides
12 Part Rule
•During each tidal period (6.25 hours) the amount of sea water that moves can be
divided into 12 equal amounts.
•When the tide begins to Flow or Ebb in the first hour, 1/12th of the tidal range will pass
through, in the second hour a further 2/12th and in the third and fourth hour 3/12th, for
the fifth & sixth hour the tidal range slows down to 2/12th’s and 1 /12th.
•So you can calculate from this that the tide is at it’s strongest in the 3rd and 4th Hour
(mid-tide).
Tides
•The sea will retreat furthest and move up the beach
furthest each spring tide (when there is a full or new
moon).
•There will be least movement of the sea during a neap
tide (usually about 7 days after a Spring tide).
•Typically a spring tide will have a tidal range of up to 7
metres whereas as Neap could be as little as three
Metres.
Currents
Current direction
When the tide goes out (ebbs) the current will move to the west.
When the tide comes in (floods) the current will move to the east.
Tide in
Tide out
How does this affect us as sea
swimmers
•Understanding tides and currents is helpful - as
swimming with the tide can sometimes make it
about 50% faster/easier for us.
•Swimming against it can make it 50%
slower/harder.
•For example it can take 20 minutes to swim with
the current between the piers but if you swam the
other way it could increase to 40 minutes.
•During spring tides these currents can have even
more power and are particularly strong mid tide.
Weather
Forecasting Weather
It’s very important before going swimming to check the weather
forecast (as well as the tide tables).
http://www.visitbrighton.com/site/tourist-information/tidetimetables
I find www.xcweather.co.uk very useful. It provides forecasts every
three hours for the next five days (including wind direction, wind
speed, temperature and whether it’s going to be sunny/cloudy/misty
etc.
Wind
The wind is an important feature of sea swimming and in most cases
creates waves.
In Brighton winds are mostly from the south west (prevailing winds)
If a wind comes from the north you will have a flat sea!
Wind from the south produces a sea with waves.
Wind from the South or South West often produces the roughest seas
(sometimes called swells)
If you plan your swims to catch the tide and you have the wind behind
you it will increase your speed significantly.
Wind
Measuring wind speed
•The Beaufort Wind Force Scale measures wind speed
between Force 0 – 12.
•0 is a completely flat mirror like sea with almost no wind.
•12 is a completely white sea with driving spray and very
poor visibility.
•Wind speed would be above 70 miles per hour.
•Wave height on the beach would be well in excess of 3
metres (and considerably higher out at sea)
http://en.wikipedia.org/wiki/Beaufort_scale
Wind
Wind
Wind
THE END