Regalecus glesne, known as the oarfish, is notable for its elongated, ribbon-like body that can reach up to 11 meters in length. It inhabits deep ocean waters, often residing at depths of 200 to 1,000 meters. The oarfish is recognized by its silvery sheen and crimson dorsal fin. Rarely seen near the surface, it is believed to play a role in the ocean's deep-sea ecosystem as both predator and prey.

Regalecus glesne, commonly known as the giant oarfish, is a species found in all temperate to tropical oceans worldwide. Its distribution includes both the Atlantic and Pacific Oceans, with noted sightings from the shores of the Mediterranean Sea to the coasts of Australia and Japan. The species is not restricted to any particular coastal region but is widely distributed across open oceans.

The giant oarfish typically inhabits the mesopelagic to bathypelagic zones of the ocean, ranging from depths of 200 meters to as deep as 1,000 meters. This species prefers deep-sea environments characterized by dimly lit waters and stable, cold temperatures around 4°C to 10°C. The oarfish is known for residing in the open ocean, away from the continental shelf.

Regalecus glesne occupies a unique niche as a deep-water pelagic teleost fish. It is adapted to life in the deep sea with a long, slender body that allows it to navigate efficiently through the water column. As a predator, it feeds primarily on zooplankton, small fish, and squid. The oarfish's elongated form and undulating swimming motion are adaptations to its pelagic lifestyle, helping it to remain buoyant and minimize energy expenditure in the vast, open ocean.