How does one determine the appropriate, i.e., quantatative
measurement, of how far up the oar shaft the water level should be
during the drive? I am interested in doing this both for sweep and
sculling oars for my team, but cannot find any numerical
representation. I could always eyeball it, but that doesn't seem very
precise.

http://www.facebook.com/album.php?aid=35883&l=a5594&id=582411512

Have a look - it's nuts in the way that only a rower could understand!