You mentioned a rescue operation. How about self-rescue? Scenario - you dumped your canoe upstream of a bad rapids. Your buddy throws you a rope, but it's hard to hang onto because the water makes it slippery. So you do a one-handed bowline around your body. You have to grasp the rope above the knot with one hand, and tie the knot (below where you're holding on) with the other.
Doc
Great point, Doc.
I don't do much sailing, but I've spent plenty of time in canoes. Logically, I know I could tie a fixed loop, but flailing to grab a rope in a strong current while keeping head above water, that could get pretty dicey.