Every morning, tens of thousands of Bangkok's most rushed, reckless or cash-strapped commuters hop onto its "khlong" boats -- plying the main canal in a speedy, if not fragrant, bid to avoid the city's notorious road congestion.

"I take the boat because it goes much faster," 18-year-old university student, Pam Olanthanyawat, told AFP before she leapt blithely onto one of the crowded shuttles on the Saen Saeb canal.

As the city of 12 million grinds to a virtual standstill at peak times, many commuters have turned to the 30 kilometre (19 mile) long canal, or khlong in Thai.

But the boats are not for the faint-hearted.

Passengers are overwhelmingly the young and able bodied -- few older people or families with children dare board the vessels, which often pull in to dock for just seconds during rush hour.

Agile men and women -- many of whom manage the feat despite perilous high heels -- leap aboard the narrow vessels and cling onto a system of ropes inside as they speed off to the next stop.

The online video sharing site YouTube abounds with footage of unfortunate passengers who are not quick or deft enough when boarding and so plunge into the foul-smelling khlongs.

One clip shows what it calls a khlong "tsunami" -- waiting passengers getting drenched as giant waves, caused by passing boats, wash over a pontoon -- and has notched up several hundred thousand hits. (http://u.afp.com/3VN)

The boats' waterproof canvas roofs are controlled by passengers themselves, who move them up and down to allow others to board and keep everyone protected from khlong water.

But it is not always entirely effective.

"My mother never takes the boat because she is too scared," said Pam as grey spray thrown up by boats travelling in the opposite direction, dripped through the canvas.

A stinky 'Venice of Asia'?

Bangkok has a vast network of canals, although rapid urbanisation means that many are now simply short disconnected stretches, while others are blocked with pipes or other objects that would prevent them being used by boats.

Tawatchai Laosirihongthong, a professor and transport expert at Thonburi University said despite their problems, the khlong boats are a draw.

"There is no 'boat jam' and the fare is cheap," he said.

There were 38 million passenger journeys on the khlong boats in 2012, according to official figures, or 100,000 per day.

At less than 20 baht, or some 0.50 cents, a ticket is much cheaper than the elevated train network for those travelling from the outskirts of the city.

Buses are the capital's cheapest rides, but with their open windows, lack of air-conditioning and propensity to get snarled in the Bangkok traffic, they are a less popular option for the time-stretched commuter.

Currently, the khlong shuttles are run entirely by a private company, Family Transport, whose fleet of 70 shuttles covers nearly 20 kilometres (12 miles) of the city's canals.

Tawatchai said the challenge is that in Bangkok's infrastructure "everything needs to be improved".

Municipal authorities are testing public boats on a supplementary 11 kilometre stretch, adding 14 new pontoons to the 27 already in use.

Bangkok is also promising more sewage and waste water treatment plants to make the khlongs a less pungent way to get around.

A recent article by the English language Bangkok Post expressed frustration that the city does not make more of its canals and main river, making an unfavourable comparison with the South Korean capital's reinvigoration of one of its waterways.

"Since Seoul can do it, why not Bangkok and our government?" it said of the Cheonggyecheon stream that runs through the heart of Seoul, where city residents can dip their feet into the water and picnic on its banks.

The Rough Guide to Bangkok said Khlong Saen Saeb was a worthwhile experience for visitors to the Thai capital, a city widely nicknamed the Venice of Asia.

"This is your quickest and most interesting way of getting between the west and east parts of town, if you can stand the stench of the canal," the guide said.

Pam, the archeology student, said her mother can remember a time when the canals were clean, but was astonished by a contemporary comparison to Italy's Venice and its renowned aquatic transit system.

"This, like Venice?" she said, with a look of disgust as she caught a whiff of the untreated sewage sloshing in the fetid canal.