Fish are aquatic cold-blooded vertebrates with fins and scales. Many species of fish are often kept as pets in containers known as aquariums. Fish are generally divided into two groups: freshwater-dwelling and saltwater-dwelling, and fish from one group are generally unable to survive in the environment of the other. There are, however, a small number of species that move between saltwater and freshwater at different stages of their lives. Humans consume several types of fish, which is a source of animal protein.
Types of fish
Here are some of the common types:
What the Bible says about fish
FISH. Creation of, Gen. 1:20-22. Appointed for food, Gen. 9:2,3. Clean and unclean, Lev. 11:9-12; Deut. 14:9,10. Taken with nets, Eccl. 9:12; Hab. 1:14-17; Matt. 4:21; Luke 5:2-6; John 21:6-8; hooks, Isa. 19:8; Amos 4:2; Matt. 17:27; spears, Job 41:7. Ponds for: in Heshbon, Song 7:4; in Egypt, Isa. 19:10. Traffic in, Neh. 13:16; John 21:13. Broiled, John 21:9-13; Luke 24:42. Miracles connected with: Jonah swallowed by, Jonah 1:17; 2; Matt. 12:40; of the loaves and fishes, Matt. 14:19; 15:36; Luke 5:6; 9:13-17; coin obtained from mouth of, Matt. 17:27; great draught of, Luke 5:4-7; John 21:6; furnished to the disciples by Jesus after his resurrection, Luke 24:42; John 21:9-13.
- "Which of you fathers, if your son asks for a fish, will give him a snake instead? Or if he asks for an egg, will give him a scorpion? If you then, though you are evil, know how to give good gifts to your children, how much more will your Father in heaven give the Holy Spirit to those who ask him!" Luke 11:11-13. 
Today there are over 10,000 species of fish, which is far more diversity than all land vertebrates. This diversity pattern can be explained by the notion that fish, being aquatic, survived the Great Flood, while many land vertebrates went extinct during this catastrophic event.
- Genesis 1:20-21 says, “And God said, 'Let the water teem with living creatures, and let birds fly above the earth across the vault of the sky.' So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good.”
And, although God told birds to fly above the Earth (in the sky), some birds just said, "Screw you, God, I'm afraid of heights." (Actually, they just evolved in such a way that they are unable to fly - such as rheas, penguins, ostriches, and cassowaries - but the first story just sounds funnier, and it brings God into the picture, so we'll go with that.) Some fish said, "We want to try!" And so God implanted mutated wings onto the Atlantic Flyingfish, which can now glide across the water.
And so God messed up Genesis, but he forgot to tell Moses (who obviously wrote it), and so now we have an incorrect account of how God created life, the universe and everything.
Will someone please add some pictures of Walking Fish and Flying Fish? Let's make this page colorful!"
- Brian Innes. The Book of Dreams. Amber Books Ltd. ISBN 978-1-905704-21-7.