Hunting sharks - for science
They are majestic, awe-inspiring and not a little bit terrifying.
But for Chris Fischer, a one-time fisherman and now a devoted conservationist, they are a mystery that needs to be solved.
Fischer leads an organisation dedicated to catching and tagging the predators, so that scientists can track their migration and mating habits.
Video Journalist Colm O'Molloy spoke with him during an expedition off the coast of Florida.
Video by Colm O'Molloy.