Swordfish is the common name for a large, highly migratory, predatory marine fish. Characterized by a long, flat bill, the lack of pelvic fins, and an absence of scales and teeth in adults. They are found worldwide in oceans, including the Pacific, Atlantic, and Indian Oceans.

In addition to the role in marine food chains, swordfish are well known for recreational fishing and cuisine, and their beauty, grace, and behavior adds to the mystery and wonder of nature. Swordfish belong to a species that likely are the fastest swimming fish in the world, including bluefin tuna, swordfish, and sailfish. Other members of the suborder include barracudas, mackerels, and snake mackerels.  

A notable characteristic of the billfishes is the remarkable ability to practice a form of endothermy, a type of warm-bloodedness where an elevated body temperature is maintained through internal means. Billfish exhibit a type of endothermy known as cranial endothermy whereby only the brain and eyes are warmed They remain "cold-blooded" in that they do not maintain constant internal temperatures and the temperature often mirrors the ambient temperature. But by being able to raise the temperature of their brains and eyes, they can have faster eye movements when hunting, which is valued when diving deep into the ocean where the water is very cold.

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What distinguish the swordfish from other billfishes are the swordfish's lack of scales and teeth in the adult, and the shape of the bill, which is depressed. The swordfish is named after its sharp bill, resembling a sword, which together with its streamlined physique allows it to cut through the water with great ease and agility. Contrary to belief, the "sword" is not used to spear prey, but rather it is used to stun prey by slashing back and forth. Mainly the swordfish relies on its great speed and agility in the water to catch its prey. One possible defensive use for the sword-like bill is for protection from its few natural predators. The shortfin mako shark is one of the rare sea creatures big enough and fast enough to chase down and kill an adult swordfish, but they do not always win, since sometimes in the struggle with a shark a swordfish can kill it by stabbing it in the gills or belly.

Swordfish grow very large, reaching a maximum size of 177 inches and 1,400 pounds. Female swordfish grow larger than males, with fish over 300 pounds mostly being female. Females mature at four to five years of age, while males mature first at about three to four years.