A teenage girl drifts in and out of consciousness, as around her the groans of her stricken family fill the chill air.

Hands reach out in a universal gesture of concern, from parent to child, from rescuer to the rescued. And voices - some in English, others not - give desperate, plaintive encouragement to hold on, just a while longer.

Warning: video contains distressing scenes

Amid the chaotic scenes of a Channel rescue played out on the deck of the Dover lifeboat, questions of nationality, of politics, of division, are dissolved by a universal human impulse: the saving of the lives of those in peril.

This is the message behind a hard-hitting new campaign by the Royal National Lifeboat Institution (RNLI), which uses body-camera footage of a rescue at sea to show the reality of the charity's mission to protect those who make the short, but incredibly dangerous, crossing of the Channel in small boats.

"Often, people are seasick, retching over the side or through fingers, making the decks slippy," one volunteer crew member says of the experience of going to sea to save lives.

"Either that or they are suffering from cold or exhaustion or dehydration.

"Others come with injuries picked up on the way. Some are missing limbs. Some are blind or deaf. Others are old and infirm. Some are pregnant. Many come with stories.

"There was the paramedic and his wife from Iran who had left after handing out leaflets demanding democracy. There was the well-dressed young man from Syria who had fled conscription.

"There was the Kurdish family from Kuwait and the Iraqi whose family had all been shot. Then there was the man who had lost his business due to war and disease.

"God’s honest truth, it’s impossible to tell saints from sinners when a dinghy is sinking in open water and its occupants are yelling and screaming for help. After bringing the people ashore, we immediately hand them over to the authorities. We are never told what becomes of them."

The harrowing footage - captured on the helmet cameras of the lifeboat crew - is from a recent call-out to five people attempting to cross the busy shipping lanes to reach the UK.

Among the casualties were a family of four, including a 14-year-old girl, believed to be from Afghanistan, who were all cared for by the lifeboat crew after being rescued from the waters.

Latest government statistics show that yesterday 502 people made the journey across the Channel in 12 small crafts, which are very often entirely unsuitable for the journey.

The volunteer crew member, who wished to remain anonymous because of abuse from a section of the public due to his actions saving asylum seekers, explained how the flimsy dinghies behave in the water.

He said: "Dinghies are always packed the same way. Women and children huddled on the thin plywood floor, men on the outside, seated on the inflated hull.

"The dinghy bottom is usually swilling with a mixture of seawater, petrol and vomit. Floating on top of this highly inflammable, rank cocktail - among the plastic bags and spoiled belongings - you might also see a foot pump and a pile of floppy bicycle inner tubes in case the boat sinks.

"This is because the buoyancy aids supplied by the traffickers are sometimes stuffed with little more than cardboard.

"Even on a mild day, somewhere on the imaginary line between the UK and France, the swell can slop about uneasily and an overloaded dinghy will flex dangerously against its glued seams.

"Coming across a dinghy in anything more than these conditions makes mouths go dry. Water respects no one. It will kill even the brightest and best in seconds."

Simon Ling, the RNLI's head of lifeboats, says he hopes releasing this footage while help people gain a better understanding of what the charity's volunteers endure as they support its mission to save lives at sea - whoever you are, wherever you may come from.

"We are incredibly proud of our crews who continue to respond selflessly to their pagers, day or night, simply to help others," he said.

"They have responded in a humbling way to this increase in demand with continued dedication, commitment and compassion.

"Each time our crews are requested to launch by HM Coastguard they do so knowing that someone's father, mother, son or daughter could end up in the water and need help.

"They understand the potential human cost so leave behind their own families and employment to go to the aid of others. We thank them for their selflessness.

"The challenges our crews face in this demanding search and rescue environment continue to evolve and we are continually developing new ways we can support our teams to ensure they have the best and most suitable care, protection, equipment, and training available. The welfare of our crews is extremely important to us."