Passenger ferries to and from the UK now are being patrolled by armed French police officers.
France introduced the sea patrols after a series of terrorist attacks, according to a marine police spokesman.
"A permanent unit has been deployed for passenger ferries since August 1," Lieutenant Pierre-Joachim Antona told AFP on Tuesday.
"The marine gendarmes will carry out patrols, which will be random but regular, with the aim of securing these vessels against the terrorist threat," he said.
The first patrol was on Monday. French officers were transported by helicopter onto the Mont Saint-Michel ferry as it entered French waters from Britain. They stayed on board until the ferry docked in Caen in northern France.
Antona said the armed patrols are similar to those in train stations across France, whose use high visibility as a deterrent.
France and Britain are currently in talks about extending patrol operations outside French waters. If agreement is struck, French officers could be present on ferries from port to port.
