If you're out doing serious and extended exercise, you might be better served with a respirator setup. The 3M 60000 series cartridges are for gasses, and you can place a P100 prefilter unit over them for particulates. Very comfortable compared to any cloth or disposable mask.Original Post Deleted
The only two downsides I can think of are that they are unlikely to enjoy being doused with salt water (I don't know how tippy a kayak is) and they might not play well with glasses.