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Narwhals sporting monitors to measure ocean temperature, salinity, and depth help scientists map hard-to-reach areas, like the cold and harsh regions around Greenland.
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Elephant seals equipped with temperature and salinity monitors have helped scientists map the Southern Ocean, as well as study how it transports heat.
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Another ocean-bottom dweller is the stingray, which could also be outfitted with depth sensors to help scientists map the sea floor.