As I heard recently, some years back polar bears were thought to be endangered, there were less than 10,000.
Today there are over 25,000.
Maybe they are drowning because there are too many ?
Since I always receive the reply "tell that to the polar bears" when I state my views on global warming (or the lack thereof) - I was intrigued by your comment - had to google it - here's a good article you can reference:
http://scienceline.org/2007/02/05/health_driscoll_polarbears/