Jack may have been grim and serious a lot of the time back in Cariff, but he's always known how to enjoy himself too, when the situation allowed. He throws himself into fun with just as much enthusiasm as he does saving the world.
"You've been missing out, then!" he declares, swooshing about a bit, just for the silky feel of the water moving against his bare skin. "Everyone should get to do this every now and then." He grins. "Especially skinny dipping!"