Migrants in Calais have sneaked into trucks or trains, and even tried to walk through the undersea tunnel in increasingly risky -- and sometimes deadly -- attempts to reach Britain.
However tighter security has stymied these efforts and authorities have reported about a dozen operations to rescue migrants drifting in inflatable dinghies in the Channel since the start of the year. In 2015, there were none.
The most recent rescue took place on June 11, when three Iranian migrants were saved from their sinking vessel. Four days early, three other migrants were rescued in similar circumstances.
Pierre-Joachim Antona, spokesman for the local French maritime authority, said efforts to cross the Channel by boat were "no longer extraordinary or isolated".
There have been rare cases in recent years of migrants drowning while trying to swim across the narrow sea, and an Afghan once built a raft with a bedsheet in a failed effort to drift to England.
But the phenomenon is now a "real and lasting trend", said Antona.
Hundreds of thousands of economic migrants and refugees have crossed from Turkey to Greece in overloaded boats SINCE , hundreds of them perishing in the process.
While France's migrant crisis is tiny compared to that faced by Greece or Germany, the slum-like Calais camp of about 4,000 migrants desperate to reach Britain is a political hot potato on both sides of the Channel.
Many of the migrants have relatives in Britain, or believe they will have a better chance of finding employment there.
The migrants' main tactic has been sneaking onto the back of trucks, initially when drivers stopped to rest and later by blocking roads and forcing their way onto the vehicles.
The crisis reached a peak in July and August last year when hundreds tried to storm the Eurotunnel site on several consecutive nights to try cross the Channel.
Security was stepped up in response to the disturbances, however recent efforts to block traffic flared again last month.
At least 26 people have been killed attempting to reach Britain since June 2015.
Antona said it had become "nearly impossible" for migrants to make it through the tunnel, forcing them to adapt their tactics.
He said that while coastguards had intercepted several boats, there was evidence that some were succeeding in crossing the treacherous stretch of water.
"We are realistic, we know there have been other attempts, successful or not," said Antona, citing "clues on English and French beaches, like small boats or life vests."
"When the weather is good you can see England from the French coast and, quite naively, one could imagine the crossing will be quick and easy but it is an absolute illusion," he added. "It is one of the most dangerous seas in the world."
High levels of traffic, strong currents and cold water mean chances of surviving a crossing are flimsy.
"The risk of a boat not being seen by a large cargo ship and being run over are enormous," said Antona.
Both France and Britain have stepped up patrols and efforts on land to curb the trend.
Patricio Martin, director of the border police in northern France, said a surveillance system had been set up along the coastline to "intercept smuggling networks even before the migrants take to the sea".
A police source, speaking on condition of anonymity, said that smugglers were demanding "up to 10,000 euros ($11,300)" for the crossing.
Antona said that the smuggler would provide a small boat, sometimes with life jackets and a telephone to call for help if needed.
"These are very fragile vessels, completely unsuited for this kind of crossing. Some don't even have engines and the migrants have to row," said Bernard Barron, head of sea rescue charity SNSM in Calais.
However there were also professional smugglers using larger, sturdier vessels that can carry up to 20 people, he said.
In May, 18 Albanian migrants were rescued from a rigid-hulled inflatable boat when the boat started to take on water. Two British smugglers who were also on board were charged over the attempted crossing.