Sharks are cartilaginous fishes meaning their skeletons are made of cartilage not bones. 2. Whale shark is the largest shark as well as the biggest fish. It can reach up to 50 feet long and weigh around 20 tons. 3. They have excellent vision and can see very well even in little light. This helps them spot their prey easily at night. 4. Sharks vary from each other in how they reproduce. Some give birth to live young while others lay eggs. 5. The smallest shark is the Dwarf Lantern shark measuring only 19 centi-meters.