Anyone who has gone swimming knows how difficult it is to move in water than it is in air. This is due to the fact that water is denser than air, which means that there are more water molecules in a given space than there would be air molecules in the same space and under the same pressure.
As an object attempts to move through these molecules, it would encounter friction which slows its movement down. Aside from this, saltwater found in oceans and seas is denser than freshwater, so it is even harder to travel through. Despite these difficulties, there are animals which can travel easily against the opposing forces of water and even hold records for being the fastest swimmers in the marine world.
1. Pilot Whale
Pilot whale (Globicephala melaena) is a large dolphin which can attain speeds of 47 miles per hour (76 kilometers per hour). Also known as blackfish, this marine animal is not only a fast swimmer, but it is also a highly intelligent one. It is known for being very social and for stranding itself on beaches.
There are two species of pilot whale: the long-finned and the short-finned. The long-finned pilot whale can grow to about 21 feet (6 meters) long, with females about three feet (91 centimeters) shorter than the males. Meanwhile, the male short-finned pilot whales grow to about 24 feet (7 meters) long and weigh over 3.5 tons (3,175 kilograms). This makes their speed all the more impressive.
2. Yellowfin Tuna
Yellowfin tuna (Thunnus albacares) is a warm-blooded fish like the bluefin tuna, typically found in warm ocean waters around the world. Although its circulatory system is not as efficient as the bluefin's, it can swim faster at 50 miles per hour (80 kilometers per hour).
This powerful marine species is not just a fast swimmer, but it is also a long-distance swimmer. This fish forms schools and often travels with other fish, porpoises, and dolphins.
3. Swordfish
The fastest swimmers in the oceans belong to the family of billfish, which include the swordfish (Xiphias gladius), named for its long, flattened beak that resembles a sword. Just like its relatives, the swordfish is shaped like a torpedo with a long and compressed body that allows it to swim through the water at up to 60 miles per hour 97 kilometers per hour).
4. Sailfish
Another member of the billfish family, the sailfish (Istiophorus platypterus) can reach speeds of 68 miles per hour (109 kilometers per hour) as it leaps out of the water. This species is smaller than the swordfish at around 11 feet (3 meters) in length, and typically weighs only about 182 pounds (83 kilograms). It got its name from its dorsal fin which stretches nearly the length of its back.
5. Black Marlin
The black marlin (Istiompax indica) is usually found in the warmer waters of the Pacific Ocean and the Indian Ocean. Like all billfishes, this marine species has a distinctive elongated upper jaw that takes the shape of a sword.
Sailfish was initially thought to be the fastest marine animal, but its record was beaten when a fisherman caught a black marlin on a line. It was claimed that the fish stripped the line off a reel at 120 feet per second (36 meters per second), suggesting that the fish was swimming at about 82 miles per hour (132 kilometers per hour).
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