Last summer, the Wee One refused to wear the life jacket we had for him for the pool. Now that he's nearly three, one is able to reason with him a wee bit more--safety belt for the car, cycle helmet for on his bike, life jacket for kayaking/sailing. And the life jacket so he doesn't sink.
A week ago I took him to SandyBottom's (aka Dawn) while we messed about with kayaks, and Dawn popped him in her Core Sound 20 Dawn Patrol. He was so excited, he swore off kayaking and now believes sail is the only way to travel (!)
This weekend, we again went around to Dawn's, complete with a new life jacket I'd just picked up at REI, thinking that this would be the way to kick start him wearing it.
Sure enough, he's hooked!