Four migrants tried to cross the English Channel aboard a makeshift raft made from two windsurfing boards that had been lashed together.
They sought to make the perilous journey on Wednesday using shovels as oars and were spotted by the Dunkirk Seaways ferry about 5.5km off the coast of Calais.
Staff on board the ferry then sent a warning to French authorities at about 12.25am.
Tired and suffering from mild hypothermia, the four people were rescued by the French navy at about 6.45am, authorities said.
[#OpÃ©ration] Sauvetage dâune embarcation de 4 migrants en difficultÃ© dans le chenal de @Dunkerque (62) par la vedette cÃ´tiÃ¨re de surveillance maritime (VCSM) Escaut de la #gendarmerie maritime sous la coordination du #CROSS Gris-nez â¶ï¸https://t.co/nBJoHTIViM pic.twitter.com/a99584WmQ6— PrÃ©fecture maritime Manche et mer du Nord (@premarmanche) June 10, 2020
They did not appear to be wearing any lifejackets or buoyancy aids, despite the low sea temperature and dangerous waters.
They were taken ashore at Dunkirk and handed over to border police.
More migrants also made it across the English Channel to the UK on Wednesday.
At least two Border Force boats, the cutter Hunter and coastal patrol vessel Speedwell, have been in operation off the UK coast.
The Home Office said Border Force intercepted three boats carrying 40 migrants.
Those intercepted, who included 31 males and nine females, said they were Iraqi, Iranian, Afghani, Syrian and Yemeni nationals.
The Home Office did not provide any information as to their ages nor how many were under 18.
At least 1,440 migrants have now crossed to the UK on small boats since the coronavirus lockdown was announced, according to data gathered by the PA news agency.
This is despite the continuing coronavirus crisis and repeated warnings of the dangers of crossing the English Channel in small boats.
Giving evidence to the Commons home affairs committee last month, former head of the Border Force Tony Smith said he cannot see an immediate end to the crisis.