By David Shukman
Environment correspondent, BBC News
Repeatedly struck by cyclones, flooding and even drought, Bangladesh is reckoned to be one of the countries most vulnerable to the effects of climate change.
MONDAY 7 SEPTEMBER: THAT SINKING FEELING
The BBC's David Shukman explains how the flood defences are repaired
I have read a lot about Bangladesh and the threat of rising seas but never thought I would feel the effects myself.
But when we visit a project to repair a breach in the sea defences around Gabura Island, the only way to get good shots is to leave our boat and join the labourers.
In the thick of it.
The process involves the men scooping up mud and passing the lumps in a human chain to be pressed into an embankment.
It is an apocalyptic scene, like something from the pre-industrial age, swarms of men toiling in the heat, nothing mechanical in sight, only loud cheers periodically keeping the work going.
That sinking feeling: We were glad of the local help to pull us out
I recall seeing how the Dutch do these things, with monster machines hauling rock and concrete.
Here it is a more elemental struggle of bare hands and mud against the sea, the reward being a chance to keep a family's hunger at bay with five kilos of rice per man per day.
To begin with I only sink in up to my ankles, the warm brown water filling my boots, something I prefer not to think about in too much detail, given that the number of people living upstream is several hundred million at least.
But as we film, the tide starts rising unexpectedly quickly and I soon notice that we are no longer ankle-deep, but thigh-deep.
Barefoot, nimble and expert, the workers know exactly where to stand to find the firmer ground.
I do not.
I try to shift my right foot but find it sinking. Soon my notebook, tucked away in my trousers pocket, is immersed; luckily my phone is in a shirt pocket.
The line of men nearest me collapses in laughter - until they see the stricken look on my face and someone hauls me upwards, Bangladeshi politeness unfailing.
I shout out a warning to Tony Fallshaw, who is shuffling towards me, burdened with the extra weight of the camera.
Despite arduous conditions the men retain a positive outlook
One of his legs disappears so deeply that he needs two people to retrieve him, arms offered in support, not hands because they are thick with mud and considered too dirty.
Work cannot possibly continue, our comedy act is far too hilarious.
Especially when producer Mark Georgiou has an idea for a shot using our waterproof camera and invites mud to be thrown at it.
Our plan was to report on Bangladesh's struggle against the sea, not slow it down.
As we leave a huge cheer goes up.
I like to think it's acknowledging how we lightened an otherwise back-breaking day; but more likely it is relief that we did not get more than one leg stuck.
On Gabura Island, under a dark sky, I encounter a new kind of victim - the commuter-refugee, people whose homes are submerged with every high tide.
Twice a day they're forced to take to their boats to travel to dry land.
Their island, nine miles long and five wide, lies between two rivers at the very tail of what begins as the mighty River Ganges and it's only habitable because it's encircled by a massive embankment.
The problem is that you can now sail straight through it.
Locals still rely on aid, four months after the cyclone
Cyclone Aila ripped open huge holes in this defensive wall and our boat just chugs through one of the gaps.
In the storm, thousands of homes were lost, 43 people were killed, dozens more went missing.
We arrive during a rising tide and although a few houses are above water, most are flooded and the fields are completely submerged. The island has become a vast, salty lake.
Ahead of the tide's peak, narrow wooden canoes carry families towards what remains of the embankment, the highest ground available.
Only a few metres wide, this narrow strip of land offers the only refuge, a packed, jostling encampment, the women's saris bright against the endless grey of the mud.
A slippery path snakes between two rows of shelters, plastic sheeting secured with string, a long line of misery.
More than 20,000 people are camped here, some all the time, others only staying during the high tides.
Four months on, they still depend on aid.
We watch as workers from Oxfam and its local partner Progoti hand out bamboo poles, plastic sheets and string, precious essentials during these monsoon months.
In the rain, the mud is so slippery it may as well be ice.
It's also sticky. As we leave, I dangle my boots over the side of the boat but not much of it washes off.
SATURDAY 5 SEPTEMBER: PEOPLE, PEOPLE EVERYWHERE
A population bigger than Mexico, crammed into a country smaller than the UK
The numbers are bewildering, so is the heat, and I hadn't reckoned on the sheer beauty of the country either.
During a four-hour drive from Jessore to Shyamnagar in the far south there isn't a single stretch without people.
The people of Satkhira live in one of the country's remotest areas
Every turn in the road brings rickshaw-riders hauling perilous loads of sacks, men straining with great lengths of bamboo, three people to a wobbling bike, forests of arms dangling from the windows of crammed buses.
I count the faces peering from the cab of a truck: there are at least eight, and maybe more I can't see.
Our cameraman Tony Fallshaw spots a scooter carrying four.
Ranked as the eighth most populous nation on the planet, Bangladesh has a staggering 156 million people - that's more than giants like Mexico and Nigeria - but packed into an area smaller than Britain.
And, as our journey takes us further south, I can believe it.
On a stop to film farmers harvesting rice, I check my watch: within 90 seconds at least a dozen people turn up to have a look at us; after three minutes there's a crowd.
We get quite an audience in a stifling roadside restaurant too, strangers sweating over plates of rice and dahl being a rare sight.
In this extremely poor country, Satkhira, the region we're in, is one of the poorest and remotest.
It didn't get many visitors until Cyclone Aila struck in May and an army of aid workers arrived.
The storm surge tore through the intricate patterns of embankments, ditches, paddy-fields and houses, its impact all the worse because every inch of this low-lying land is cultivated or lived on.
One surprise: the energy of the multitudes here. Through floods and hunger, power cuts and poverty, life goes on in this deceptively pretty landscape.
Another surprise: a man perched on the back of a bicycle has a mobile phone pressed to his ear.
I switch on my Blackberry.
It works - even on a boat.
And one of the first e-mails reaching me here, beyond the last road on this distant, battered shore is a press release.
The prime minister of Bangladesh, it says, speaking at a climate conference in Geneva, has just warned how vulnerable her country is to natural disaster.
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