The roar of the engine cuts out and everything is silent. I hold my breath and scan the waters for a sign of life. Suddenly a glistening black and white tail flicks up and into view. "Go! Go! Go!" screams the Skipper and I plunge into the icy waters. As I swim I look through my mask into the deep and see a giant directly below me - there's no turning back now, I'm swimming with humpbacks.