A form of underwater diving that requires a diver to hold their breath underwater without the help of any gear (e.g. scuba equipment) to help them breathe.

Technology that helps a diver swim and breathe underwater. One or two tanks of compressed (squashed) air are connected by a hose to the divers mouthpiece, and the tanks are strapped to the divers back.

Reef sharks live in tropical (warm) waters near coral reefs. They are apex predators, which means they sit at the top of the food chain, and are therefore very important to the health of reef ecosystems as a whole.