Sharks are "cold-blooded" (poikilothermic) animals, meaning their body temperature is the same as that of the water in which they live. The term cold-blooded is misleading, however, because sharks living in warm water are "warm-blooded" in actual temperature.

Some fast-swimming sharks in the Mackerel shark order (for example the mako and white sharks) can actually raise their core body temperature somewhat above that of their surroundings. In these sharks, heat generated as they swim is conserved by a special vascular network surrounding the muscles. This network helps to conserve heat in the body core, rather than allowing it to dissipate into the cooler water.

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