A man has died after suffering cardiac arrest onboard a boat attempting to reach the UK.
The vessel turned back towards Equihen beach on the French coast yesterday morning.
A nurse tried to resuscitate the man but was unsuccessful.
French authorities have now launched an investigation into the circumstances.
A spokesperson for Doctors Without Borders, also known as MSF, has criticised authorities on both sides of the Channel.
Jacob Burns said: "Yet again we have a tragedy in the Channel, that is the consequence of the deadly, costly and ineffective security policies implemented by the UK and France."
Later on Saturday, a lifeboat carried migrants who have made the voyage into the Port of Dover.
Photographs showed them huddled under blankets and orange life jackets on board.
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Provisional statistics from the Home Office suggest almost 24,000 people have arrived on small boats in the UK so far this year.
Towns and cities across the UK have seen protests in recent days, primarily outside hotels believed to be housing asylum seekers.