Questions on ships

[Wander]

I've been reading one of Lionel Casson's excellent books on sailing in ancient times, and I see that it was common for the hulls to be sheathed in lead. I can see that this would serve multiple purposes: waterproofing, protection (from barnacles and teredo worms, at least), and as a form of ballast. What I don't know is exactly how it would look: was this simple grey metallic lead? And how far above the waterline would it usually go? (Keeping in mind that any extra weight above the waterline fights against the stabilizing effect of ballast.)

Oh, and how exactly was it fastened to the hull? Nails?

I've also seen at least one relief (can't remember the source right now) showing a ship with the rowers apparently facing the bow, which would involve them pushing the oars rather than pulling. Most others show a conventional position facing the stern and pulling. Was this sometimes done? Maybe rowing backwards, for example? Or could it simply be an error on the part of the artist?

Thanks in advance for any answers.