[Dog of Hellsing]

The thing about the Lakes is that there are various pools. Some are small to mimic lakes, others are extremely large to try and mimic the sea. There are also a mix of freshwater and saltwater lakes, to further cater to whether a specific Pokemon would live in one kind of water or the other.

But meh, if someone wanted to go through the trouble of splitting the Great Lakes into two seperate water areas, I don't really mind. It's just that it would be kinda silly to have two of the same habitat.