It was an image of one of the explorers falling into icy water.

NEWYORKER: Show The Monster

The four-year-old swivelled around several times before falling backwards into the water in his enclosure.

BBC: Candles by Knut's enclosure

His sister, who Barthel identified as 16-year-old Madison Wallace, at one point went in after him and ended up falling into the surging water.

CNN: March 16, 2013 -- Updated 0041 GMT (0841 HKT)

"This is a really significant event and we need to learn from it, not just in Washington but around the country, " Hersman said after taking a boat ride on the Skagit River below the dramatic scene where a truck bumped against the steel framework, collapsing the bridge and sending two vehicles and three people falling into the chilly water.

NPR: NTSB Says Wash. Bridge Collapse Is Wake-Up Call

Four men are critically ill after falling from a ship into the water during an exercise drill at the Royal Portbury Dock near Bristol.

BBC: Four fall from ship at Royal Portbury Dock

But he was afraid of falling asleep and dropping into the gator-filled water, so he duct taped himself to a branch.

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