I have a story about that, it's not really on topic but oh well. I was on a river tour in Kakadu on the East Alligator River and there were crocs everywhere. The Aboriginal guide had just finished telling us how we couldn't do this of a night because they'd be jumping in the boat with us when there was a huge bang and he yelled "holy ****". I was at the back of the boat and it looked like a prairie dog convention in front of me, heads popping up and looking around. He'd hit a submerged log and the shear pin on the prop broke. No problem, there was a smaller spare motor which he said would get us back just a bit slower. It started, we went 20ft and it coughed, died and wouldn't start again. Then we spent a nervous few hours while he went looking for help and they came and towed us back.