NRS safety gear:
Pre-made pin kit: http://www.nrsweb.com/shop/product.asp?pfid=1817&deptid=963
The Wall pulley (see Yates Gear above) is my personal favorite. It's got a sealed bearing and won't bind up on a tyrolean traverse (I've tested this).
If you’re ever in a low-head dam or hydraulic, swim for the bottom. That’s where the water heading downstream is.
Low head dam safety (must watch):
Love this video. While it’s a natural feature, this is how sticky low head dams are. Love the lack of safety too. http://video.google.com/videoplay?docid=9168227802071776104&vt=lf&hl=en