Sharks vs. Fish: Key Differences Every Diver Should Know
Sharks are specialized cartilaginous fish with skeletons of cartilage, five to seven gill slits, and often sharp teeth, while “fish” usually refers to the broader group of bony fish whose skeletons are made of bone.
Many divers lump every finned creature under “fish” because both groups swim, breathe through gills, and live in water. The difference only matters when you’re logging sightings, estimating bite risk, or choosing dive sites.
Key Differences
Sharks lack swim bladders, rely on oil-filled livers for buoyancy, and have replaceable teeth. Most bony fish adjust depth with gas bladders, sport scales that overlap like shingles, and possess just one gill cover per side.
Which One Should You Choose?
If you’re drift diving reefs, expect colorful bony fish. For pelagic night dives, look for sharks cruising in open water. Choosing the right guide and gear depends on which group you hope to encounter.
Examples and Daily Life
Your logbook notes: “10 whitetip reef sharks” versus “cloud of anthias.” Knowing the difference helps buddies understand current and depth preferences, saving air and time on every dive.
Can a shark ever be called a fish?
Yes, sharks are technically fish, but saying “cartilaginous fish” keeps your logbook precise and fellow divers informed.
Do all fish have bones?
No; sharks, rays, and skates have cartilage instead of bone, placing them in a separate class from typical bony fish.