Helicopters Landing on Yachts..

I know this sounds a left field topic but my interest was sparked as I watched the helicopter pilot land on the back of Ilona a month or so in front of my place at night on Sydney Harbour....I was just thinking what skills it must take and wondered if there had been any accidents landing on the back of these massive yachts.....
I mean when I look at Le Grand Bleu I always worried about that sailing yachts mast that sits on the back of it....
I found this shot of one landing on Paul Allen's Octopus and it looks like a hairy landing to me.....Anyway ....
http://community.webshots.com/...IDipB