There are more than 20,000 kinds of fish, all designed by the Creator to fit right into the particular part of the ocean, lake or stream where He has placed them. Like birds, animals and humans they must have oxygen, and this they get from water, which contains a certain amount of dissolved oxygen. Water enters the mouth, and as it passes over the gills, the oxygen is absorbed into the blood stream. Carbon dioxide is formed during the breathing process and released into the water.
There are two principal kinds of fish. Most have bony skeletons supporting their bodies, but others, such as sharks and porpoises, have no bones (except in their jaws). Instead, their bodies are supported by a covering of tough, gristly, elastic cartilage. Fish are slim and streamlined, but there are interesting exceptions that do not resemble fish as we think of them. These may look like seaweed, rocks, the muddy bottom of their homes, or many other things. Thus they are hidden from enemies and also able to surprise unwary sealife that becomes their food. These camouflages did not come by chance. They were designed by their wise Creator.
Tails and fins are for swimming and guiding through the water. Most tails are vertical (up and down), divided into two parts and represent their source of power. But in a few the tail is flat and solid. Combined with the work of the tail are the fins, some behind the gills, some underside or on, the back and some near the tail. Each species has its own arrangement—some with the "dorsal" fin running the full length of the back and others with very small dorsals.
Then there are the important scales, representing their armor. However, some, such as certain bullheads and most catfish, do not have scales and instead have smooth, slippery skins. Scales usually cover the fish from head to tail, much like shingles over the roof of a house, overlapping in rows. They are hard, made of bony tissue and provide good protection for the flesh underneath. A fish's age can be determined by counting the yearly rings on a scale, the same as is done with the rings of tree trunks.
To most of us everything beneath the surface of oceans and deep lakes is mysterious, but nothing is hidden from the One of whom the Bible verse says, "Neither is there any creature that is not manifest [visible] in His sight: but all things are naked and opened unto the eyes of Him with whom we have to do." Heb. 4:1313Neither is there any creature that is not manifest in his sight: but all things are naked and opened unto the eyes of him with whom we have to do. (Hebrews 4:13). This reminds us that not only does the Lord God see every fish, small or great, but also sees each one of us at all times and knows all about us. What a happy thing it is to trust in Him as our personal Savior and know how real that watchful, loving care is!