All this month the BBC World Service is travelling along the rivers of Bangladesh as part of a major project to track and debate climate change and other issues.
The BBC's Alastair Lawson, one of those on board the vessel, the MV Aboshar, which has travelled through some of the areas devastated by last week's cyclone, describes what he witnessed.
17 November - VILLAGE OF DEATH
We travelled from the south port town of Mongla to the cyclone-hit village of Sharonkholur and I am afraid it is no exaggeration to say that what we saw was a hellish scene.
Many of the flimsy huts were destroyed during the cyclone
I suppose the first thing that struck me was the ground - muddy and grey like a First World War battlefield. My next impression was the fact that not a single house was standing.
It was as if the village had been bombed, flattened by an almighty fist from above.
Household debris, the bloated bodies of dead livestock and torn-off strips of corrugated iron were scattered everywhere.
Adjoining the village was a huge river, the kind for which Bangladesh is famous.
In the fast-flowing currents, people on boats were still pulling bodies from the water.
The water was littered with all the tell-tale signs of disaster: discarded fishermen's nets, pieces of housing and the wreckage of boats.
One huge freight ship we saw had been tossed like a discarded child's toy onto the river bank.
Every single tree in the area had been destroyed, many falling on top of the flimsy straw huts where the villagers lived.
Next, and saddest of all, were the gravediggers, still burying people when we arrived there. And all the time the haunting noise of women mourning, wailing the loss of their loved ones.
The body of a dead boy lay at one side of the path leading into the village, still not properly laid to rest.
The villagers themselves had nothing left, only the clothes they wore.
Because the paddy fields had been destroyed, many had not eaten since the storm struck.
We spoke to Mohammed, who was digging graves.
"Already I have dug eight graves today," he said, "but still we are finding more and more dead people."
18 November - SHROUDED IN DARKNESS
At night, the town of Mongla is shrouded in darkness, because the cyclone cut all electricity lines.
In some respects the lack of light reflects the sombre mood of people in the town after the worst storm in Bangladesh for over a decade.
Mobile telephones work, but only intermittently.
The most striking thing about the approach road to the town is the fallen trees.
Villagers are taking the clean-up operation into their own hands
Everywhere along the road they are uprooted, in most cases falling on telephone lines and power cables.
Equally striking was the way local people removed the trees from the road. Within 24 hours most had been sawn up, by hand, and laid in neat piles by the side of the road.
While travelling from Mongla to rejoin the BBC boat at Barisal we came across a contingent of army engineers repairing a broken ferry.
The officer in charge, Col Entimal, tells me it is the worst storm he can remember and the authorities are struggling to cope.
But when asked if foreign help is needed in the clear-up operation, he becomes more cagey.
"We are capable of reaching all the affected areas," he says defensively.
But when asked to give a timescale the colonel is more non-committal.
It appears increasingly obvious that this is a battle for the army is ill-equipped to fight.
19 November - HUMAN SUFFERING
We have seen so many distressing things since the cyclone struck.
Parents robbed of their children, people who have not eaten for several days, homes destroyed.
As we head further south, the chief concern seems to be over water.
The further south we go, the more the suffering seems to increase. Villagers say that their tube well water has dried up, and their surface water has been contaminated by dead livestock.
Added to that is the danger of water-related diseases, chief of which is cholera.
20 November - AID SLOW TO ARRIVE
Everywhere along the river bank in the south-west of Bangladesh, people line up waiting to receive supplies.
Money has been pledged but little has yet to arrive on the ground
When out boat passes, they cry out pleading for us to stop.
It is a pitiful sight and sound, and belies claims made by the government and international NGOs that they are reaching all the affected areas.
As I write this I can see six people frantically rowing towards the BBC boat in the hope that we will give them something to eat.
We are warned that if we go ashore we risk being surrounded by people and triggering food riots.
The UN and the west have pledged millions of dollars in aid. But so far there is little sign of it arriving, and it results on the ground that matter.