Well, he obviously wouldn't need to bring aquatic animals, and if he had taken young representatives there would have been plenty of room. AiG says that insects could have survived on floating vegetation mats, but I think that's a little far-fetched.
Where AiG goes wrong however, is claiming that speciation can occur and that "kinds" could have been very broad categories of animals. This likely comes from the failure to realize that the species classification denotes that they can only produce viable offspring with fellow species members. For instance, I have seen a picture from their museum of a model of a giraffe-okapi blend. This would be impossible, as they are different species. AiG compares this to the types of dogs, but he seems to fail to realize that the breeds are all the same species.
Actually he would need to bring every fresh-water aquatic animal. The water that covered the Earth would be saline, since salt water makes up well over 90% of all the water on the planet. Fresh water fish would die.
and if he had taken young representatives there would have been plenty of room.
There's plenty of room for two of every wild and seven of every domestic animal on a boat 450 feet by 75 feet? Are you kidding me?
Easy to explain: rapid evolution. Actually every creationist believes in evolution, if by that one means variation as in genetic drift and degradation. The type of evolution where constructive mutation is involved is what creationists reject.
I don't describe myself as a creationist, I'm a skeptic about all explanations. None of them make sense to me.