An AFP journalist saw how the group carried the large dinghy on their shoulders across the beach near Gravelines in northern France, floating it on the relatively calm Channel waters before clambering aboard.
Many of the migrants were wearing red life jackets, and women and children could be seen among the mostly male group.
The new departures in calm and sunny weather come despite joint French and British efforts to disrupt people-smuggling gangs.
Last month, French police swooped on people suspected of involvement in a November 2021 mass drowning of migrants attempting to cross to Britain.
So far 10 suspects face charges -- including manslaughter -- over the 27 deaths of people aged seven to 47.
Only two people survived the disaster, the worst since crossings picked up in 2018, which sparked fresh tension between London and Paris.
Attempts by Britain to begin deporting asylum seekers to Rwanda for processing -- which is intended to serve as a deterrent -- have been held up by court action.
French interior ministry figures recorded 777 attempted crossings from January 1 to June 13 this year, involving over 20,000 people -- up 68 percent on the same period in 2020.
France claims its security forces prevented 61 percent of attempted crossings this year, up 4.2 percent from the period last year.