I used to portage my canoe on a small trailer behind my bike. I would then load the bike and trailer into the canoe, and float downriver. When I pull that so-loaded canoe out of the water, does it stop being a maritime vessel?

This Buick-manufactured device could be considered a maritime vessel that just so happens to be carrying the mechanisms necessary for self-portage. And I’d be happy to sell you the placards needed for that.