The fastest aquatic animal is the black marlin (Istiompax indica), known to reach speeds of up to 82 miles per hour (132 km/h). This impressive speed allows it to evade predators and catch prey. Black marlins inhabit warm ocean waters and are highly sought after by sport fishermen for their strength and acrobatics when hooked. Their streamlined body and powerful dorsal fins contribute to their remarkable speed and agility underwater. Other fast swimmers include the sailfish and swordfish, but the black marlin holds the record for the fastest, showcasing the incredible adaptations of marine animals in the pursuit of survival.