Thousands of human bodies end up in the sea every year as a result of accidents, suicides or dumping.
In recent memory, tens of accidents have happened at sea in different parts of the world, with the majority of the victims ending up dead on the surface of the sea or at the floor.
On June 10, 2009, Brazilian authorities recovered 16 bodies from the Atlantic Ocean after an Air France crash that had happened 10 days earlier.
In 2014, a Sewol ferry from Incheon port in South Korea sank while enroute to Jeju Island with more than 300 passengers on board.
It took more than three months to recover 304 of the bodies in what turned out to be a highly mismanaged exercise.
After the devastating 2016 Tsunami in Japan, it took more than four months to recover 250 bodies from the sea.
Finding survivors lost at sea is usually a race against time, with the high possibility of starvation and hypothermia.
But when the rescue mission takes longer than can sustain life underwater, focus often shifts to retrieving the bodies.
Such is the case at the Likoni channel in Mombasa after a car slid off MV Harambee ferry on September 29 and fell into the ocean, taking with a woman and her daughter.
While diving to the bottom of a murky sea is treacherous enough, retrieving a body and bringing it to the surface is a much more complex task, replete with risks that could potentially claim the life of diver(s).
So, what does it take to conduct this highly delicate and dangerous mission?
Locating the scene
This helps the rescuers to narrow their scope and to search in the relevant places.
Retrieval of bodies after accidents occurring in the open sea is harder as rescuers must determine the correct spot to search.
That said, ocean waves are strongest in the deep blue sea, and bodies can be swept many miles away from the scene of the accident.
This explains why some body parts of sea accident victims have been swept ashore months later, thousands of miles from accident scenes.
Planning the dive
Retrieval from the sea is a delicate and expensive exercise that needs skilled planning.
A team has to be assembled at a command centre, often in a vessel on the surface, to coordinate the mission.
Emergency services have to be on standby should an accident occur during the operation.
In the absence of a submarine, individual divers have to swim through the water to locate the bodies. While doing this, they must have the necessary kits.
An oxygen tanks allows the diver to breathe while underwater.
Flippers help the diver to glide through water with ease.
Where the dive is prolonged, taking several hours, snacks help to keep the diver energised.
A headlamp is necessary where water is murky and visibility limited to a few metres.
A guiding rope attached to the vessel on the surface of the sea helps to monitor the movement of the diver and to drag them onto the surface in the event that of an accident.
Where there is a wreckage and rubble following an accident, divers have to swim with caution.
Submerged fishing nets and other debris compound the risks, and divers can get entangled in them while groping in the dark of the water.
Sea creatures, especially sharks, are a big threat to divers.
Recovery and rescue
Once a body has been located, the most delicate phase of the mission starts – fitting it into a body bag.
For bodies that have just sank, lifting them to the water surface is easier because they are generally intact.
It is different for bodies that have stayed underwater for long, because they are likely to be at an advanced stage of decomposition.
The overriding objective is usually to lift a body to the surface with minimal damage. To do this, absolute care has to be paid to the tissues to avoid tearing them apart.
The design of body bags for carrying drowning victims is different from ordinary bags used on land.
Late Australian deep diver David Shaw says the body bag for use in the water has to have a netting bottom.
This allows water to flow out of the bag and to break friction with the water, a concept known as sea anchor effect.
Divers often swim up the surface while dragging the body.
Risks remain alive during the entire mission.
Some divers have died during a recovery mission.
In 2005, highly skilled scuba diver David Shaw succumbed to respiratory complications owing to high pressure underwater when retrieving the body of Deon Dreyer from a cave in South Africa.
Dreyer had drowned in 1994, nearly 11 years before his body was recovered.
David Shaw may have succeeded in the delicate mission, but he paid with his own life.
Fatigue, vertigo and convulsions are known to kill people who have been underwater for long.
Divers often rest at different stages during the ascent to the surface, which allows them to change gas as well.
While 100 metres sounds a short distance, navigating this distance underwater can take several hours due to the high pressure below the surface.
According to Gail Anderson, a forensic entomologist at Canada’s Simon Fraser University, having an understanding of how bodies disintegrate in the water can give rescue divers a sense of what to look for.
This, he adds, helps to ‘‘manage the expectations of family members of those lost at sea’’.
Anderson says that when a body submerges when oxygen conditions are tolerable, larger sea creatures are likely to swim to them and scavenge on them. This allows smaller aquatic creatures to eat up the remaining parts.
When oxygen levels are low, large animals don’t get to the body, which increases the possibility of finding it almost intact.