The important thing about wool is that it continues to keep you warm even when it’s soaking wet.
Other natural fibers don’t do this. In fact, quite the opposite. Campers and boaters are usually familiar with the phrase, “cotton kills.” If you’re wet in cotton or linen, your clothes actually sap heat from your body.
If you sink in a lake in late October like I did today, staying warm is important. I was rescued long before I would’ve actually died, but cold makes your muscles seize up, which isn’t good if you have to swim to land.
Which brings me around to life jackets. If the water’s cold enough, you may only have five-ten minutes until your muscles seize (today I probably had 40-60, more than enough time to get to land if I hadn’t been picked up), and you’ll drown.
In a life jacket, even in extremely cold water, you can float semi-conscious for perhaps another 30 minutes or so before you actually freeze to death, which is usually when someone rescues you.
What’s more, you probably know that moving around on land warms you up. Jumping jacks, jogging in place, etc.
In water, moving actually makes you colder. You need to stay still curled up in a ball, which you can only do in a life jacket.
In wool AND life jacket, you’re warm, and your head’s above water, which is pretty much your only and entire goal.
If you’re allergic to wool, synthetics are available specifically for this purpose. I know I always say natural fibers are the way to go, but when it comes to safety, wear what protects you!