Fish are cold blooded, live in water and are covered in scales. They breathe through gills located on the sides of their heads. Their gills take oxygen out of the water around them so they can breathe. Their limbs, if they have any, are in the shape of fins and do not have digits. They exhibit greater species diversity than any other group of vertebrates, with over 32,000 known species.


A large, distinctive, and predatory sea creature, the swordfish is an ocean dweller of impressive size and appearance. Their scientific name, Xiphias gladius, comes from the words for ‘sword’ in Greek and Latin, which describes them perfectly as these fish have a long, flat bill that looks very much like a long blade. They are also known as broadbills in some countries, and though they look similar to other fish like the marlin, with a comparable sleek and rounded body type, they’re actually the only members of the Xiphiidae family.


Hammerhead sharks, which belong to the family Sphyrnidae, are some of the most unique looking creatures in the ocean. There are ten distinct species of these sharks, which most people recognize by their distinctive head shape; a flattened, extended structure that’s called a cephalofoil.  (A related and slightly different hammerhead species, the winghead shark, is classified under the family name Eusphyra instead.) Hammerhead sharks tend to prefer warm water living, so they’re usually found in ocean habitats that are close to coastlines and continental shelves.


Although eels look like snakes, they are fish and belong to the order Anguilliformes, of which there are about 800 species. The term "eel" is also used for some other similarly shaped fish, such as electric eels and spiny eels, but these are not members of the Anguilliformes order. The main species of true eels include American eels, European eels, moray eels and conger eels. Most eels are predators and feed on fish, snails, frogs, octopuses, crabs, lobsters and mussels. Eels feed during the night and rest during the day. These aquatic creatures rely on their excellent sense of smell to hunt for prey.


Blowfish, or pufferfish, are found in tropical and subtropical ocean waters and are known for their ability to inflate to make themselves inedible to predators. Some species also have sharp spines and contain toxins to protect themselves from predators. Blowfish are in the family Tetraodontidae, which are primarily marine and estuarine fish of the order Tetraodontiformes. They go by many names, including: blowfish, pufferfish, puffers, balloonfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads and sea squab. They are closely related porcupinefish, which have large external spines.


Clownfish, or Anemonefish, are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species are recognized. In the wild they are known for forming symbiotic relationships with sea anemones. The most commonly known clownfish species is orange with white markings, but clownfish are found in many different colors and can also differ in shape. Depending on species, clownfish are overall yellow, orange, or a reddish or blackish color, and many show white bars or patches. The largest can reach a length of 7.1 inches, while the smallest barely reach 3.9 inches.


The whale shark (Rhincodon typus) is a slow-moving filter feeding shark and the largest known fish species. The whale shark holds many records for sheer size in the animal kingdom, most notably being by far the largest living nonmammalian vertebrate. The largest confirmed individual had a length of over 41 feet and a weight of more than 47,000 lb. Unconfirmed reports of considerably larger whale sharks exist. The whale shark is the sole member of the genus Rhincodon, and the family Rhincodontidae. The species originated about 60 million years ago. Whale sharks are found in tropical and warm oceans and live in the open sea, with a lifespan of about 70 years. Whale sharks have very large mouths, and feed mainly on plankton.


Sharks are members of a group of almost exclusively marine and predaceous fishes. There are about 250 species of sharks, ranging from the 2 feet pygmy shark to 50 feet giants. They are found in all seas, but are most abundant in warm waters. Some may enter large rivers, and one ferocious freshwater species lives in Lake Nicaragua. Most are predatory, but the largest species, the whale shark and the basking shark, are harmless plankton eaters. Dogfish is the name for members of several families of small sharks; these should not be confused with the bony dogfishes of the mud minnow and bowfin families.


Seahorses are marine fish belonging to the genus Hippocampus of the family Syngnathidae. They are found in temperate and tropical waters all over the world. Seahorses range in size from 16 mm to 35 cm. They are notable for being the only species where the males get pregnant. The seahorse is a true fish, with a dorsal fin located on the lower body and pectoral fins located on the head near their gills. Some species of seahorse are partly transparent. Seahorse populations have been endangered in recent years by overfishing. The seahorse is used in traditional Chinese herbology, and as many as 20 million seahorses may be caught each year and sold for this purpose.


Dasyatidae is a family of rays, cartilaginous marine fishes. Dasyatids are common in tropical coastal waters throughout the world, and there are fresh water species in Asia (Himantura sp.), Africa, and Florida (Dasyatis sabina). Most dasyatids are neither threatened nor endangered. Dasyatids swim with a "flying" motion, propelled by motion of their large pectoral fins (commonly referred to as "wings"). Their stinger is a razor-sharp, barbed or serrated cartilaginous spine which grows from the ray's whip-like tail (like a fingernail). It is coated with a toxic venom. This gives them their common name of stingrays.