It was daylight and I was on watch. We were about 300nm off the E Coast of Australia near the Lord Howe Seamount Chain. Our tow gen, which is normally suspended by ropes from our stern pulpit, banged into the stern pulpit. This sometimes happens in big following seas when the tow gen propeller surfs a wave and slackens the line. When it happens, we jam ropes or other soft things between it and the stern pulpit to prevent damage. This time I sat staring at the stern pulpit for a second because the seas weren’t that big. The tow gen banged again against the pulpit. I thought maybe something was fouling the propeller and looked behind the boat toward the prop.
I saw a huge dorsal fin surface, moving sideways to our path. As it crossed where the tow gen prop was trailing, the back of the shark also rose out of the water for a second. I caught only a glimpse of it and I am terrible at estimating size and distance but I can tell you that I have never been in the water with a shark that big.
I squealed. Carol raced up from down below. And we watched the shark, now under water, pacing the tow gen prop, then falling further back but still visible in the waves pacing our boat. I took some video but of course the camera was downstairs initially and so it was too late when we brought it up (the story of cruising and wildlife usually). There is a grainy moment in the video where Carol and I see the shark with our eyes, but this screen shot (below) just shows something darkish in a wavelet.
When we pulled the propeller upon landfall in Coffs harbour several days later, it had candy stripe strips of paint removed from its shaft as if something hard/sharp had been pressed against it while it was spinning. Was it the shark’s skin when it bumped it? Did it actually bite it? We have no idea. There was also a gouge out of the propeller blade.
We had heard that sharks hit tow propellers but we had never spoken to anyone who had actually had it happen. I can state for the official record that they DO!