What is part lion part fish in Greek mythology?
Sea-lion. It sounds confusing (since there is a marine mammal known by that name) but that's what they were called.
You will find the WikiAnswers category 'Myths and Folklore' at the link below. Another place for mythology questions would be Ancient Religions, since Greek and Roman "mythology" was actually part of the religious beliefs of ancient Greeks and Romans. You can find Greek Mythology at 'History Politics and Society/Ancient History/Greek Mythology'.
Learning about Greek mythology helps us understand the beginnings of Western civilisation. It also helps give us a wider perspective of religion. Another good reason to learn about Greek mythology is because much great literature, religious practices and stories in the west are based from it. Further, the stories are very colorful and entertaining. Greek mythology was the basis of the ancient Greek religious beliefs and an important part of their culture.