Most sharks are cold-blooded. Some, like the Mako and the Great white shark, are partially warm-blooded (they are endotherms). These sharks can raise their temperature about the temperature of the water; they need to have occasional short bursts of speed in hunting.
Most sharks are ectothermic, which means they are cold-blooded. Their body temperature typically matches the temperature of the surrounding water. However, some sharks can elevate body temperature above that of the water in the surroundings. A good example of a shark that can do this is the great white. Read on from www.sdnhm.org/archive/kids/sharks/faq.html#cold.