Four people died on Thursday off the coast of northern France as they tried to board a small boat to cross the Channel to England, taking the number of such deaths this year to six.
The two men and two women were swept away by the current near the village of Equihen-Plage, regional official Francois-Xavier Lauch said.
Another person was treated for hypothermia, he said, while 37 people were taken into the care of the emergency services.
The nationalities of the four dead were not yet known, he added.
A large number of emergency service vehicles and rescuers gathered on the beach, with people standing by a first aid post nearby, many wrapped in thermal blankets and a few wearing life jackets.
The migrants were trying to board a so-called "taxi boat", officials said, referring to dinghies that leave shore discreetly and almost empty before picking up dozens of migrants wading into shallow waters.
The latest deaths show that smugglers continue to "enrich themselves" by "exploiting the misery and distress" of migrants trying to reach Britain, said local prosecutor Cecile Gressier.
