Column SFF Bestiary Meet the OG Sea Serpent: The Giant Oarfish In a world full of weird and wonderful beings, the oarfish is right up there. By Judith Tarr | Published on September 29, 2025 A History of the Fishes of the British Islands, Jonathan Couch (1862). CCA 2.0 Comment 0 Share New Share A History of the Fishes of the British Islands, Jonathan Couch (1862). CCA 2.0 It never ceases to amaze me how rich this planet is with life, and how much of it fills the seas—and how little we still know about its full range and variety. One of the least explored regions of the oceans even now is the one between the light and the dark, from about 600 feet to 3500 feet down, between 200 and 1000 meters. This is the mesopelagic zone, where only 1% of incident light is able to penetrate, where the pressure becomes too intense for the human body to tolerate. Creatures of these depths and below sometimes rise to the surface, and occasionally wash up on shore. They’re seldom alive by then, and it can be hard to identify the remains. Even when they are living, a human swimming or riding in a boat may have to guess what they’re seeing. Before the invention of the underwater camera or the submersible (either manned or unmanned), there was no way to observe these animals in their native environment. Sailors out on the ocean told tales of enormous serpents that swam in the sea. Like the Kraken with its many arms and the Leviathan that swallowed Jonah, these myths and legends had a basis in fact. Leviathan, of course, was a whale, and the Kraken a giant squid. As for the sea serpent, there are a number of possibilities, including the venomous sea snake and various forms of eel including the conger and the moray. But the best candidate may be the giant oarfish. In a world full of weird and wonderful beings, the oarfish is right up there. It really is a giant: ten to thirty feet long (three to ten meters), with legends telling of oarfish that reach fifty feet (fifteen meters) or more. It’s a fish of many names: oarfish, ribbon fish, king of the herrings, and my favorite, the doomsday fish. In Japan it’s believed to foretell earthquakes; if an oarfish washes up on shore, that’s a warning to get to solid ground. It looks like a mythical beast: long, serpentine, ribbon-thin, with a blunt, short head crowned with spines, long narrow pectoral fins that trail beneath, and a dorsal fin that runs all the way from its head to its distant tail. The body is silvery with dark spots and a shimmer of bioluminescence, and the dorsal fin is usually red. That long narrow fin ripples constantly, propelling the fish through the water. It swims vertically, head up, mouth open, feeding on krill. It’s a filter feeder, and it travels up and down with its prey, rising as high as a few dozen feet below the surface, and descending to the borders of the abyss. Its body has evolved to survive in the crushing pressure of the deep. It has no scales; its skin is smooth and covered with a layer of guanine, its flesh is gelatinous (and apparently tastes disgusting), and its bones are soft and flexible. It’s able, like a lizard, to shed part of its tail if attacked, a process called autotomy, though unlike a lizard it won’t regrow the lost section. This is an elusive fish. It’s seldom seen alive, but it doesn’t appear to be rare, let alone endangered. It’s found in warmer waters all over the world, even in the Mediterranean, where River Monsters’ Jeremy Wade had a remarkable encounter with two in 2016. He’s fascinated by how they move: “It doesn’t flex the body, just the fins undulating like a wave.” It’s weirdly beautiful to watch. It’s a gentle fish. It’s not aggressive, it’s not dangerous; it doesn’t even have teeth. Despite its reputation as a harbinger of doom, it’s never harmed a human. It’s not hard to see why sailors would spin legends around this huge, serpentine creature. Its size and its strangeness stand out, even in an ocean full of giants.[end-mark] The post Meet the OG Sea Serpent: The Giant Oarfish appeared first on Reactor.