Divers

[Carlton Bach]

he is using an inflated skin to swim across a moat or a river

Yes, that was my first thought too, cf. the picture below. However, I think the man on the first picture appears to have something in his mouth. Nevertheless, it is indeed possible that he is not a diver but an inexperienced swimmer. Do you known any publications on this guy?

About this guy, how on earth would it be possible to float across anything sitting on that? It's instable - you'd fall off as soon as your feet don't touch the ground anymore.
I've inflated a lot of things for my kids - I know. :?
Now, if he would hang on to it with his arms, OK. But either the artist heard of it and depicted the technique all wrong, or the guy is doing something different than floating.

It looks like he is holding on to something. Maybe a boat?

Damnit, I need to get to London with my digital camera...