Look at the photo, it's hard to describe that as anything but a barrel: https://dynaimage.cdn.cnn.com/cnn/q_auto,w_634,c_fill,g_auto...

In particular, it lacks any conventional boat elements like a method of propulsion or steering.

He is clearly milking the label for all it's worth though, the GPS tracker ID was "diogene" (French for Diogenes of Greek philosopher living in a barrel fame) and his sponsors included several manufacturers of wine barrels (https://www.boutes.com/), who apparently also helped build the thing.