The Wool Pooh is one of the most mysterious symbols in the book. Is it real? Is it imaginary? Oh, and what on earth is it? We don't have all the answers (gasp!), but we do have a few thoughts.
First, let's take a look at the name. The whole Wool Pooh thing gets started when Grandma Sands tells the kids to stay away from Collier's Landing because a little boy got caught in a whirlpool there and drowned. Only Grandma talks with a Southern accent, so when she says "whirlpool," it sounds like "wool pooh."
Joey, curious little one that she is, asks Byron what it was that got the boy and Byron tells her it was the Wool Pooh, Winnie-the-Pooh's evil twin brother who hides underwater and waits to snatch kids and drown them. Um yeah, that's the scariest thing we've ever heard. But it's pretty clear to us that Byron is making this up. Kenny thinks so, too, but he has a pretty vivid imagination, so he isn't 100% sure. Still, he goes to Collier's Landing anyway with one eye out for the Wool Pooh.
Then, when Kenny is drowning, he thinks he sees the Wool Pooh:
That's when he came swimming real slow out of the deep, and even though my head was underneath the dark water I could see him coming right at me. He didn't look like he was related to Winnie-the-Pooh at all, he was big and gray with hard square-looking fingers. Where he should have had a face there was nothing but dark gray. Where he should have had eyes there was nothing but a darker colder-looking color. He grabbed my leg and started pulling me down. (13.50)
Could Kenny be hallucinating the Wool Pooh because he's running out of air? Could it be that he really does see dark, mysterious shapes in the water and that imagination of his makes him believe it's the Wool Pooh? Could the Wool Pooh really exist? Kenny's pretty sure the Wool Pooh is there to bring him to his death, kind of like the Grim Reaper:
[Byron] was very wrong when he said the Wool Pooh was something he'd made up. If he'd ever had his ankle grabbed by it he'd know it was real, if he'd seen the way he was crouched down, crawling around in the dust and smoke of the church in Birmingham he'd know it wasn't some made-up garbage, if he'd ever seen those horrible toes he'd know the Wool Pooh was as serious as a heart attack. (15.101)
Whatever else it might be, the Wool Pooh is definitely a symbol for death. It shows up first when Kenny is about to drown and then again at the church after the bomb goes off. Kenny is the only person who sees the Wool Pooh, and both times, he's really scared. Maybe Kenny's fear combined with his awesome imagination create this monster.
Why? Well, it's probably easier to understand death if it's at the hands of a monster. No one wants to think about the fact that a person can just die while swimming or going to church on a perfectly normal day. Maybe the only way Kenny can accept the idea of death is to turn it into a monster he can physically fight off or run from. If there's something there to fight, then he has a chance; but if death can just happen, then what can anyone do?