The shortest distance across the Channel is from
Shakespeare Beach, Dover, to Cap Gris Nez (the headland halfway
between Calais and Boulogne). This distance is 18.2 nautical miles
which is approximately 21 land miles. There are 2,000 yards or 1852
mtrs to a nautical mile. Most of the England/France swims start
from Shakespeare Beach between one hour before high water and one
hour after high water, although the pilots do start at other times
and places, depending on the tide, the weather conditions, and the
swimmer's ability. France/England swims (when these are permitted
by the French authorities) usually start from Cap Gris Nez or its
immediate vicinity. The traditional start time is about 3 to 4 hours
before high water, although this can also vary considerably depending
on the tide, weather, swimmer and pilot. With the use of computerised
plotting for course calculations and the modern electronics on the
pilot boats, start times and places can be evaluated before the
swimmer enters the water, and the best choice of route made.
The FLOOD TIDE flows from the South West from 1.5
hours before HIGH WATER to 4 hours after HIGH WATER DOVER. The EBB
TIDE flows from the North East from 4.5 hours after HIGH WATER to
2 hours before HIGH WATER DOVER. As the tidal cycle is a little
over 12 hours from one high water to next, the times of high water
change every day getting later as the days progress.
Because of this movement of water from one place
to another, the Dover Straits are prone to strong tidal flows, and
a large rise and fall in water between high and low tide. To complicate
things a little more, the position of the moon relative to the earth
and the sun affects the gravitational pull that is moving the water.
When the sun, moon and earth are in line we have maximum tides known
as SPRING TIDES. This is every 14 days on the new moon or the full
moon. When the moon is at 90° to the earth, we have minimum
tides known as NEAP TIDES. This is every 14 days when the moon is
in its first and third quarter. Thus we have 14 day cycles with
the tides going from Springs to Neaps and back to Springs. From
tidal atlases and nautical almanacs we find that at Dover: Mean
High Water Springs is 6.7 metres. Mean High Water Neaps is 5.3 metres.
For Channel swimming - Spring tides are 6 metres or more and Neap
tides are 6 metres or less. Most swims take place on the Neap tides.
These are the slacker tides and show as a more direct line on the
chart. The lower the tide, the longer the period of slack water
when the tide turns, and the slower the tidal flow. Approximately
6am and 6pm (GMT).
This is between 57°F and 64.5°F (14°C
to 18°C). The temperature is around 57 to 60°F at the end
of June beginning of July, then rises slowly to 64/65°F by the
end of August, then it usually drops by a couple of degrees before
the beginning of October. There are however exceptional years like
1995 when the water temperature reaches 67°F (19°C).
Air temperature and chill factor.
This varies considerably depending on the weather
and the hours of daylight. The longest day is about the 21st of
June, giving daylight from about 0330 to 2200 hours. This decreases
to 0600 to 1900 hours by the end of September. Body heat is lost
from the parts of the swimmer exposed to the air (head and shoulders,
etc.). The air temperature is higher during daylight hours, therefore
the longer the day, the greater the period of higher air temperature,
and the smaller the loss of body heat.
The English Channel is one of the busiest shipping
lanes in the world, with approximately 600 vessels moving up and
down them every day, and ferries, hovercraft, seacats and jetfoils
crossing between England and France at very regular intervals. Because
of this international shipping lanes have been agreed and their
areas marked on the charts. On the English side we have the South
West Lane which is for vessels travelling down Channel to the Atlantic.
On the French side we have the North East Lane for vessels which
are travelling up the North Sea areas. Crossing from Dover there
is the English inshore traffic zone which is about 5 nautical miles
wide, followed by the South West Lane which is approximately 4 nautical
miles wide. In the middle is an areas known as the Separation Zone
which is one nautical mile wide. Then there is the North East Lane
which is approximately 5 nautical miles wide, followed by the French
inshore traffic zone which is 3 nautical miles+ (depending on where
you are) to the French beaches. The English Coastguard, stationed
at Langdon Battery Dover, and the French Coastguard, stationed at
Cap Gris Nez, keep radar and VHF watch on the whole of this area
liaising with the vessels using the Channel. They broadcast navigational
bulletins every half hour and log vessels using the lanes to co-ordinate
the movements and monitor safety. Channel swims differ from other
swims of this distance by their complexity and the localenvironment.
This is why it is one of the ultimate challenges.