There were sea dragons at one time. The Bible talks about them and even describes them as breathing fire. Job 41:19-21 is describing an aquatic beast called Leviathan. It says that "out of his mouth go flaming torches, sparks of fire leap forth. Out of his nostrils come forth smoke." Verse 21 says that "his breath kindles coals and a flame comes forth from his mouth." Certain kinds of dragons did exist at one time.