As the flooding that has made millions destitute across Pakistan moves down through the country, the BBC's Ben Brown travelled by hovercraft and helicopter to follow relief efforts in southern Sindh province.
Like a river that became a sea, the Indus now sprawls for miles.
The "great mother", as it has been affectionately known because of the fertility it has brought to the land, has now drowned hundreds and left millions homeless.
Sindh is the worst-hit province in Pakistan, and some of the places we visited there have only been flooded in the last few days as the monsoon waters have moved inexorably south.
As the UN secretary general said, this is a tsunami in slow motion.
Take the village of Goth Mohammed Ismael, for example.
Like so many villages here, it's turned into an island, and we found its people bobbing up and down in the filthy brown floodwater, as they waded and swam back to their homes to try to salvage what possessions they could.
Goth Mohammed Ismael was only flooded last week.
Amina, a mother of six, says four children died when the floodwater hit.
"The flood came at one o'clock in the morning," she told me.
"I was feeding my baby at the time. There was panic everywhere. People were crying and asking each other for help."
A man called Hamed Bux emerges from the water with a bundle on his head.
It contained just a few clothes, all he had managed to salvage from his home.
"These clothes are all I have left in the world, please help us," he said.
Help is coming, but painfully slowly.
Most of the flood victims have still received no aid at all.
On the floodwater near Sukkur, we travelled on a Pakistan Navy hovercraft that was looking for victims to rescue, or to help with relief supplies of food and clean drinking water.
Many people want to stay in their homes, even when they are marooned or completely submerged by water; they are determined to protect the only possessions they have left.
Commander Zahid Iqbal and his crew pass relief supplies to the hungry, thirsty and desperate from the hovercraft.
"Our hovercraft can reach places where a normal boat cannot," he says.
"Not in my life have I seen anything like this. But I don't have any doubt in my mind that, with the help of the entire world, we'll come out of this situation."
Helicopters are a vital part of the aid operation here too, though for now there are far too few of them.
Four have been provided by the Afghan National Army (ANA).
You might think the Afghans have enough problems of their own, but they have been quick to help their Pakistani neighbours.
Fighting for aid
We flew on a mission with the ANA, dropping relief supplies from the air near Sukkur.
It was too dangerous for the helicopter to land - partly because there's very little dry land any more, and partly because desperate people would surround the aircraft and could get hit by the rotor blades.
So instead the helicopter crews drop box loads of high-energy biscuits from the air.
We watched people run and swim through the floodwater to get to the aid drops, and sometimes fight each other for the rations. It is survival of the fittest.
The boxes being dropped are from the UN World Food Programme, and were originally meant for the people of Afghanistan.
On the ground too in Sukkur, aid distributions are chaotic.
The Sindh police force organised one - with supplies they had paid for with their own salaries.
Sadly it descended into chaos, with flood victims pushing and shoving each other so badly the distribution had to be abandoned.
"I can't blame them," said Assistant Inspector General Javed Iqbal.
"They need food to give to their families tomorrow."
Even so, it was tragic to see one flood victim walk away with blood streaming down his face.
He'd come to collect food for his family, and left with a gash to his head.
A number of governments and aid organisations are appealing for donations to help those affected by the flooding in Pakistan.