There was a large submarine high power cable buried or on the bottom
somewhere nearby. What you felt was the induced current caused by the
large electric field emanating from the cable.

Over40pirate wrote:
A few years ago while cruising, I was weighing anchor, and when I got to the
chain (no windlass then) I was shocked, not by what was on the hook, but as in
electrical shock. I dropped it and pulled it in again with the same shocking
results. It wasn't a killing shock, and as the hook was clear of the bottom, I
motored off enough with the hook in the water to be sure I didn't pick up a
live cable, then hauled it aboard, getting shocked as I did it.
Before I tell the cause, any guesses?
K