The article mentions that as many as 500 ships travel through the channel each day at speeds of 25-knots or so and that these container ships take about a mile to stop. The obvious concerns sited are potential collisions between boats and swimmers.
I do believe their concerns for 21-years ago they banned channel crossings from their side which illustrates an antagonism towards the swim rather than any sort of political or economic machinations.
From the Guardian:
"... Danish company DFDS, which runs a service between Dover and Dunkirk, wants the Maritime and Coastguard Agency to oversee swims instead of the Channel Swimming and Piloting Federation and the Channel Swimming Association."We are concerned these crossings are unregulated and growing at an expedient rate. We would like to see it regulated by the MCA," said DFDS passenger director Chris Newey.The company's concerns will be echoed by Deputy director of the French Coastguard Jean-Christophe Burving in a BBC documentary tomorrow, Inside Out South East, in which he calls for the swimming route to be banned entirely, according to the BBC. ..."[Link]
A container ship can costs as much as $50,000 a day to rent when the economy is humming to probably about $10,000 today. No one wants an accident. I think will careful permitting and mass, staggered, start I am sure something could be worked out for swimmers and the French.