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!).
Slide 4
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, 1/12 th of the
tidal range will pass through, in the second hour a further 2/12 th
and in the third and fourth hour 3/12 th, for the fifth & sixth
hour the tidal range slows down to 2/12 th s and 1 /12 th. So you
can calculate from this that the tide is at its strongest in the 3
rd and 4 th Hour (mid-tide). Tides
Slide 5
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. Tides
Slide 6
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 out Tide in
Slide 7
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.
Slide 8
Weather Forecasting Weather Its very important before going
swimming to check the weather forecast (as well as the tide
tables).
http://www.visitbrighton.com/site/tourist-information/tide-
timetables 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 its going to be
sunny/cloudy/misty etc.www.xcweather.co.uk
Slide 9
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.
Slide 10
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
http://en.wikipedia.org/wiki/Beaufort_scale