I wouldn't even
have a pool with a little child running around. I just couldn't stop myself from worrying constantly. Hell, we had a little pond in the back of a house we moved into when I was 6 (my sister was like 2), and my parents simply drained it to avoid all risk.
We had a hot-tub, but it had a cover that was so heavy that if you could lift it, you were probably old enough to be in the tub anyways.
Oh, and GAH: unless you have your eye on your kids 24/7, there will ALWAYS be opportunities for tragedy to occur. It's not a matter of bad parenting (necessarily)...bad choices, perhaps (like having the pool in the first place without a cover, say) but it's certainly not as matter-of-fact as you're making it.