The article says he plans to do the entire dive without surfacing, and that it will take him around 8 hours.
"...expects to complete the dive within eight hours. An additional two hours for decompression at the French coast will be needed,.."
There may well be reasons why the dive needs to be completed deeper - perhaps optimum progress at depths where surface current can be avoided etc.
Looking at the charts - it's feasible that this record attempt could be planned for a 'true' scooter/scuba crossing along the bottom, rather than shallow submerged, as the depths are ~20-40m:
Looking at the chart (below), there's a bunch of cross-channel pipelines/power cables. Perhaps the plan is to track these along the bottom, to ensure navigational accuracy?
Tides and current will be decisive factors (as they are with the regular cross-channel swimming attempts). For reference, the fastest verified swim of the Channel was by the Bulgarian Petar Stoychev on 24 August 2007, in 6 hours 57 minutes 50 seconds.
The English Channel is approximately 19nm/38000 yards/35 km wide. It is narrowest (18.2nm) between Shakespeare Beach (Dover) and Cap Gris Nez (South of Calais). However, accounting for tide/current, a
swimmer would expect to swim about 20 nm - 37 km.
Channel tides are strong and change direction, approx every 6 hours. They flow to the NE from about 1.5 hours before high water to about 4.5 hours after high water (flood tide). Then they turn and flow SW from 4.5 hours after high water to 1.5 hours before high water (ebb tide). These tides can flow at up to 4 nautical miles per hour. The tide gets later every day by about 30 to 50 mins and change in height and flow speed every tide.
This impacts the crossing greatly, depending on whether a neap or spring tide is in action. For instance, on a 5.3 meter neap tide a swimmer (approx 12-18 hour crossing time) will be carried about 7 to 7.5 nm up Channel on the flood tide and then come back 7.5 to 8 miles on the ebb tide. On a 6.8 metre spring tide the swimmer will be carried about 13 nm up Channel on the flood tide and then come back 15 nm on the ebb tide.
This means the tide will shape the crossing into a long curve, or curves, depending on the rate of progress. For swimmers (at a slow pace) the distance traveled up and down Channel is about the same and generally cancels itself out. This probably will not hold true of a
propelled attempt - as the faster crossing pace may require deliberate off-set in course (fighting the current) rather than 'going with the flow'. Otherwise, they'd be swept north/south and have to complete a much greater distance crossing.
There is also a high chance that surface support will be required - by legislation, if not by the divers themselves. The Straights of Dover is the busiest shipping lane in the world, and governed by international law. For cross-channel swimming attempts (and attempts to set records in other "irregular craft") support vessels are typically required by British and French maritime authorities (for purposes of tracking/de-confliction) and have to be supplied through verified agencies (CSA and CSPF).
Previous record was a relay... this new attempt will be solo...
English Channel - Wikipedia, the free encyclopedia
[TABLE="class: wikitable, width: 1"]
[TR]
[TD]20 August 2011[/TD]
[TD]First Crossing by
Sea Scooters[/TD]
[TD]A four-man relay team from Scarborough, North Yorkshire, headed by Heath Samples LL.B Hons, crossed from Shakespeare Beach to Wissant.[/TD]
[TD]It took 12 hours 26 minutes 39 seconds. It set a new Guinness World Record.[/TD]
[/TR]
[/TABLE]
Nautical chart - Dover to Calais:
