Ok I tried and I failed... I think it is because I throw a punch or two before clicking on the sword icon top right.... I was dealing like 15 damage each hit so I don't think I was dealing too much damage, just the peace thing I guess.
But yes with the boat, it is really safe. The only issue is running from the hitchpost to the water but luckily I'm not far (I take 2/3 hits before being in the boat). And for everyone wanting to try it too, it is really safe if you have take aim to have ip before using chop for example.
EDIT : And just to be sure, the horse was in the hitch post for a long time, and he was agitated (like angry, and when I tried to rope him, he didn't want to), so I used the "attack!" button to aggro it to tame it.