Funny how this keeps happening everywhere, not just on rivers. Last month at my shop I watched a guy spend two hours wrestling a lawnmower deck off because he didn't check where a bolt was seized first. Quick look saves a whole lot of headache, but people always think they'll get lucky. It's like that old saying about measure twice cut once, just applied to machinery instead of wood.
On the Snake River last spring, we hit a submerged log pile. A simple depth check would have caught it. It cost us two days of downtime for a five minute scan.