rogue waves

A commercial fisherman was battered by one of those rogue waves you hear about in the tall tale chronicles of the sea. He's one experienced boater who lived to tell about it. Rogue Wave - True Story

I have a curiosity about rogue waves so I did a little research. I have seen large swells that seem random and infrequent and it's a real problem if you're running in a following sea and you don't see them coming. I can't imagine these walls of water some as high as 90 feet. It seems freakish...