There are various predatoy animals around; tigers, sharks, komodo dragons, etc. You can be the bait so long as you kill it. I got the achievement during the first mission from Dennis. After skinning the boars and collecting the green and red plants, I went into the water for the blue plant. Rather than fast traveling back to Dennis when the game said to, I swam on to the next blue plant and was promptly attacked by a crocodile. Once I killed it, the achievement popped.
Be on the lookout and above all, survive!