That's a really good reason why you should carry at least one fixed blade or one-handed folder within easy reach AT ALL TIMES. Preferably two, on different locations.

A number of people have died in a situation similar to yours. Falling into a fast flowing river, getting entangled in rope, branches, a submerged tree or some such obstacle is no joke. I've heard of a guy who drowned because his boot lace got caught underwater on a rock and he couldn't take it off. Eventually his buddies pulled him out but it was already too late. Folks have burned to death because they crashed their car and couldn't unfasten the seatbelt before the vehicle caught fire. Lots of not-so-pleasant scenarios that can happen almost any time.

Also, keep in mind that any gear that sticks out of your general silhoutette too much is likely to snag on something. I often see hikers who hang all kinds of stuff on their backpack, everything from cooking pots to bags, pouches and whatnot, probably just because it looks cool. Which I think is pretty unwise for the reasons just stated, not to mention it makes crawling through some dense bush unnecessarily tiring.