The Maritime Prefecture of the Channel and the North Sea said one person was found dead on the beach of Wissant, near Calais, on Thursday morning after the discovery of a boat filled with water.
Two other people were found with them suffering from hypothermia.
French authorities said they were treated by emergency services before being taken to a local hospital.
It comes after another migrant died attempting the dangerous crossing on Wednesday.
It is believed the person was unconscious when they were pulled from the water and pronounced dead as rescuers returned to the dock.
Another has been reported as missing.
French authorities said more than 400 people were rescued during a French-led rescue operation in the Strait of Pas-de-Calais on Tuesday night and into Wednesday.
UK authorities on Tuesday rescued or intercepted 456 people who had navigated busy shipping lanes from France in small boats.
Prior to that at least 19,756 people had already reached the UK so far this year, bringing the total to more than 20,200.
This is more than double the total for the whole of 2020.