The Commerce Clause in the Clean Water Act

This is really a narrow and specific question. It's just about wetlands touching or adjacent to more traditional navigable waters. But certainly the commerce clause issue was in the background here. Justice Thomas asked if there's a body of water contained entirely within one state, how can you really say that that's part of interstate commerce? And I think importantly, all of the justices, even the liberals on the court seem to key in on that precise problem.