There are over 6,000 types of fish found in our ocean waters.  A fish is a cold-blooded animal.  Their body temperature can adjust to the environment around them.  Almost all of them lay eggs.  A flounder may lay 1,000,000 eggs, a cod 9,000,000 eggs, and a sunfish 300,000,000 eggs, but not many of these eggs hatch.  The eggs fish lay vary in size from very tiny to that of a shark which can be several inches long.   Most fish lay their eggs in the oceans waters, but one unique fish swims back to freshwater streams to lay its eggs - salmon.  The salmon fight their way up through the currents, jumping over rocks and sometimes even waterfalls.  When they finally reach their destination the salmon lay their eggs and then die.  In size, fish range from tiny (smaller than aquarium guppies) to the whale sharks which can grow to measure 45 - 60 feet (if you stood the whale shark on its tail it would be as tall as a 5 story building).