I have capsized in a rigid kayak on a river many times...which is to be expected and wearing a PFD is a no-brainer in that environment (for most people anyway!), but I certainly didn't expect to roll my big fishing kayak (a model frequently used for off-shore coastal fishing) a few years ago while fishing a small lake with Ive.
What happened?
Well, for the first time I elevated its seat to its highest position (fished from it for years in the lowest position because it just felt more stable that way), and I positioned a large gearbag full of stuff I really don't need right behind that raised seat....which raised my center of gravity significantly. I'm a fairly tall guy (6'2" 225 lbs, with a long torso, built like an elderly Adonis), and that really aggravated the center of gravity situation. The anchor hanging on a Scotty anchor holder off the stern didn't help matters either, because it rotated like a pendulum as the kayak rolled..
Yeah...the Adonis part may be a slight stretch.
All it took was a reach for a fly snagged in a lillypad next to the boat to instantly roll the kayak over....and I found myself looking up at the kayak deck from below. The water wasn't all that cold (warm spring, late May, small lake).
Of course I was wearing my PFD, and I bobbed to the surface like a duck, surveyed the wreckage, and yelled to Ive down the lake for a hand to help straighten the mess out. At no time was I in any danger....the PFD allowed me the luxury of sorting things out rather than focusing my efforts at staying afloat.
There so many excellent PFDs around these days....comfortable and with pockets to hold many of the small items essential while flyfishing, and if used to do so strongly reinforces wearing a PFD.