Warm ocean water can be a killer for coral reefs, and AOML recently developed a new inexpensive sensor to drastically improve our ability to measure and monitor changing temperatures on reefs at an unprecedented scale. The low cost sea temperature sensor, known as InSituSea, costs roughly $10 in parts to produce while providing high accuracy (0.05-0.1 C) in measurement. With a production cost that is 10% of an off-the-shelf temperature sensor, colleagues have expressed strong interest in deploying the InSituSea sea temperature sensor at coral reefs around the world.