Looks like Mark decided to go with the second option I listed: a human blockade across the river. Hmm… does Cliff mean veteran boat captains or boat captains who were military vets? I’m pretty sure they are not necessarily the same. And Mark seems confused between land masses and bodies of water (panel 4).
Don’t get me wrong here, but isn’t Mark exceeding his mandate? He was tasked merely with establishing the source of the zebra mussel infestation. But as usual, Mark goes in head first to right another wrong of human interaction with nature. Not that this is a bad thing: It would be splendid if more of us took a more active role, for example. So, I’m thinking that Mark has already submitted his report to the magazine and now feels free to stage this protest on his own, without implicating the magazine if things go wrong. Just a theory, of course!
One more thing: A big difference from the old incarnation of M.T. is that now, Mark happily works with other people, rather than pretending he can do it all on his own. That’s a good thing, but too bad he did not try to work with Duck Duck Goose Shipping to solve the problem in the first place.