The Hibernia platform is uniquely designed to resist the impact of sea ice and icebergs. It can withstand the impact of a one-million tonne iceberg with no damage. It can withstand contact with a six million tonne iceberg, estimated to be the largest that can drift into that water depth and only expected once in 10,000 years, with repairable damage.
I saw a pix of this project at an oil show in Calgary some years ago.
Couple months ago....I fished right near this rig in the GOM...
http://www.bing.com/images/search?q=Perdido+Rig&qs=n&form=QBIR&pq=perdido+rig&sc=8-11&sp=-1&sk=#view=detail&id=DC74DD8B721FBABB68A77093E4E14F7E806E64A1&selectedIndex=0