The Brahmaputra is like life itself,” declared Pamkaj Kumar Das, skipper of the MV Mahabaahu. “There are perils at every twist and turn, streams flow in from many sources, they separate and re-join, and reach the finality of the ocean in so many channels that we cannot say that any is the true path.” Blimey. I had climbed to the wheelhouse to ask questions about navigation, dredging and depth of draft. But this was India, so really I should not have been surprised by a sudden elevation of the prosaic to the mystical. “Yes, this is a mystic river,” chuckled Mr Das, uncannily reading my thoughts as he steered a careful course between driftwood and sandbanks under the eye of a marigold-garlanded Ganesh, the elephant god revered as a mover of obstacles.

Perhaps the real miracle was that this understatedly plush, 23-cabin river vessel – OK, let’s call it a cruise ship – was sailing these waters at all. Brahmaputra means ‘son of Brahma’, making it not only a rare example of a male river, but the offspring of none less than the creator of the universe. His lifespan begins in the glacial womb of Mount Kailash on the Tibetan plateau and ends in the Ganges delta on the Bay of Bengal. In between, the Brahmaputra hurtles through the Himalaya before spilling on to the broad plains of Assam where, come monsoon time, he turns savage. There are frequent reports of villagers drowned in writhing torrents, and every year this season leaves behind an altered riverscape: islands changed in size and shape; unfamiliar currents surging through unseen depths and shallows.

“You could say we have taken a leap of faith,” said Sanjay Vasu, the Delhi-based mountaineer-turned-entrepreneur who has pioneered the Brahmaputra’s first cruising route. Sanjay had the Mahabaahu (meaning ‘mighty arms’, as a synonym for the river) purpose-built in Kolkata; in 2012 he sailed her up through Bangladesh to Assam. Here he persuaded the government to dredge and maintain a 2.5m-deep navigational channel, in return for a stake in the project. Now, during the placid period between October and April, the Mahabaahu cruises the Brahmaputra, providing a completely new way to experience the cut-off, far north-eastern state. There is not, nor has there ever been, a river journey remotely similar anywhere in India.

The wide pink yonder – My February journey began with a flight from Kolkata to the little airport at Jorhat in eastern Assam. From here the Neemati Ghat boarding point was 20 minutes away via a dusty jeep track through dun-coloured fields of harvested rice stubble. The five-deck, 55m-long Mahabaahu looked a bit out of place, roped and bridged by a gangplank to a crunchy sand spit in the middle of nowhere. My fellow passengers on the week-long downstream journey to Guwahati, Assam’s biggest city, were an affable bunch of Australians, Americans and Europeans. Sanjay was aboard too, because he still felt the need to keep a close eye 011 his new venture. So were ebullient young Payal Mehta from Mumbai, a professional naturalist hired to help us with the wildlife, and her erudite Keralan colleague Shatzil Khan in the role of cultural interpreter. At the first chink of dawn we sailed off into the wide pink yonder. I found it tricky getting my head around the vastness of the Brahmaputra, 14km wide in places, and ‘braided’ – it splinters into streams that meet again, forming islands.