Bangladesh, Nov. 26 -- Helicopters buzzed above the waves and vessels were already scouring the cold waters when French maritime rescue volunteer Charles Devos added his boat to the frantic search for a flimsy migrant craft that foundered in the English Channel, killing at least 27.

What Devos found was gruesome. But not, he later sorrowfully acknowledged, wholly unexpected. With migrants often setting off by the hundreds in flotillas of unseaworthy and overloaded vessels into the busy shipping lane crisscrossed by hulking freighters, and frequently beset by treacherous weather, waves and currents, Devos had long feared that tragedy would ensue.

That came this week, with the deadliest migration accident to date on the dangerous stretch ...