"FBI star Derek Hedlund nearly died after being cut by a crab.

Hedlund told Page Six that he was helping a pal move a Jet Ski in Red Bank, N.J., in July when the crustacean clawed at his foot, leaving a tiny cut -- and it turned out that the water he was wading in was infected with the “flesh-eating bacteria” Vibrio.

Hedlund told the outlet that his foot swelled up alarmingly, and at one stage a doctor said to him, “You see this line on your leg? That is the [vibriosis] spreading up your leg. You can literally see it.”

Medical staff even told the actor that if it reached a certain point on his leg, they’d have to amputate it to save his life.

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Derek Hedlund recalled the time he nearly died after being cut by a crab. (IMDB)

To make matters worse, Hedlund told Page Six he got the call to return for the second season of “FBI” while he was in the hospital, and -- not wanting to risk losing the gig -- promised producers that he’d be on set in just a few days. He says he discharged himself “against medical advice” to attend a wardrobe fitting, and showed up to the shoot on crutches a couple of days after leaving the hospital.

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To his horror, the script had him chasing “terrorists” through Central Park. He said that while the shoot was excruciating, “I did what I needed to do, and I’m still alive.”

This article originally appeared in The New York Post.