Experts established in the 20th century that sharks were prevalent in the world’s oceans more than 350 million years ago. Many of the different species are medium size and reach around five to seven feet long. Some sharks are fairly rare (great white), while others are common (bull shark) and many are torpedo shaped. Those over six feet should be considered a relative danger, however, sharks often receive unfair bad publicity. They are not quite the “man-eater” that many believe them to be. Some sharks in the 21st century are critically endangered, and this publication explores these, as well as the other species, which make up the 30 families of these impressive ocean creatures.