I've heard that carpet tacks have worked for at least one cruiser
The more thought I gave to the electric
fence idea, the less I like it (and I didn't like it to start!). I remember many years ago when I put up an electric
fence around our vegetable garden to keep out the wildlife. I trained our dog to stay away from the fence -- and she did, at least while we were watching. One day when we were on the other side of the fence our dog must've gotten curious, because she let out a yelp and retreated onto the porch. Thinking that she had forever learned her lesson, we comforted her. The very next day, while I was watching, she went right up to the fence and sniffed it. You can imagine what happened next! That time she wouldn't leave the porch for a week, and kept clear of the fence forever after.
My point is that if I were a thief (I maintain I'm not, but probably a lot of thieves do too), and I encountered an electric fence, what are the odds I'd simply move on? I'd want to investigate (like my dog, but hopefully without sticking my nose out). And take retribution.... I would much rather have someone steal from my boat than sink her.