A couple I used to know are doing a circumnavigation on their Morgan Out Island 511. The 51 foot ketch has a folding keel which was severely damaged in the pacific after a collision with a humpback whale. They have interrupted their circumnavigation and returned to Sweden to make some money for the rather expensive repairs.
http://futurewinds.se/Fiji.htm
What was left of the keel.
(http://i1375.photobucket.com/albums/ag441/snowhound2/_DSC4926_zpsix6loiwx.png)
Suppose it matters just how big your boat is.
When CVN-70 hit whale off the coast of southern California back in the early 1980s, the whale lost!