I have used the knife on my PFD only once in a (semi) emergency. My son, on one of his first trips in a solo canoe, had drifted off into some overhanging branches and gotten a dangling fishhook stuck in his PFD, very near his face.
Thinking about it I have most often used the knife to cut fishhooks and lures from streamside trees. One eagle-eyed friend excelled at discerning flies hanging from branches on our local trout stream.