Approximately 600,000 sea birds die each year by getting caught on hooks used in line fishing. A device called the Hookpod, invented by a UK company in Devon, has a clever solution to this problem. The fish hook is covered by a case so birds cannot get hooked. At a certain depth (below the diving depth of indigenous birds) a mechanism is triggered to release the case which floats to the surface and is retrieved to be used again. These lesson ideas provide an interesting practical idea to use a particle model to explain density and pressure in a gas. Students will then take part in a STEM design challenge to make a device to respond to a pressure change at a particular depth of water.

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