Channel crossing is usually critically aided by timing tides that help suck you out when leaving England, and suck you in as you approach France.
https://www.channelswimmingassociation.com/swim-advice/chann...
https://www.channelswimmingassociation.com/swim-advice/chann...
France/England swims are no longer permitted. When the French authorities permitted these they usually started from Cap Gris Nez.