"And yet, creationists want me to believe that a 450 ft. (minimum) vessel of ALL wood construction was able to withstand a storm of 40 days "
It's silly indeed. But keep in mind they simply claim it was God's intervention and from there move to something like "unlike evolutionists, at least we admit we have faith."
That's what it's like when you debate to their way of thinking. I find it best to focus on the idea that the ark somehow had to make a pit stop in Australia to specifically drop off the Kangaroos. It's difficult for them to argue that this was God's plan.