Steve-O Jumps Off a Bridge from a Moving Trampoline

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Steve-O wasn't satisfied to just jump off a bridge ... instead, he earned some style points by throwing a trampoline into the mix, and he's lucky to be alive.

The former "Jackass" star was in Tampa, FL Saturday pulling off the new stunt -- leaping off a high bridge into the Intracoastal Waterway from a trampoline mounted to the back of a pickup.

Seconds after his leap, Steve's friends shouted ... he could be dead. As it was, surviving was NOT pretty.

As for WHY in the world he did this? He's Steve-O.