Early November, pregnant giant hammerheads arrive off Bimini, in the Bahamas and Shark Week's Dr. Tristan Guttridge wants to know why? And he and his team even perform the world's first ever ultrasound on hammerheads to find the answers.

Paul De Gelder returns to Shark Week with Dr. Jonathan Werry and Andy Casagrande to unlock the mysteries of the new great white hotspot, Isle of Jaws. And on their journey, they make a startling discovery that causes them to re-think everything.