One moment you’re enjoying a calm ocean swim, the next you’re face-to-face with a giant, googly-eyed, pancake-shaped UFO that weighs more than a car and lays 300 million eggs at a time. Meet the mola mola, the world’s heaviest bony fish, a creature so bizarre, so cartoonishly oversized, and so mind-blowingly fertile, it makes even the wildest sea monsters look like shy goldfish.
Bigger Than Your Ute—and Stranger Than Fiction
The mola mola, also known as the ocean sunfish, doesn’t just break records, it shatters marine biology expectations. Growing up to 3.3 metres long and 4.2 metres tall, the biggest recorded individual tipped the scales at a mammoth 2,300 kilograms (that’s roughly the weight of a rhinoceros or a Toyota Land Cruiser). And while most fish have streamlined bodies for speed, the mola mola looks more like a dinner plate with fins, making it a hydrodynamic oddity that cruises rather than zooms.
Despite their clumsy looks, they’re seasoned travellers, diving to depths of 800 metres in search of jellyfish and other gelatinous meals. But after chilling in the abyss, they return to the surface and float on their sides, like a giant sea pancake, soaking up the sun. It’s a strange sunbathing ritual that helps them regulate their body temperature. Yep, it’s like your weird uncle who needs a nap and a tan at the same time.
A Fertility Machine with No Off Switch
If there were a Guinness World Record for overachieving mums, female mola molas would win it by a nautical mile. These leviathans can produce up to 300 million eggs in a single spawning season, the most of any known vertebrate on the planet. To put it into perspective, that’s more eggs than all the chickens in an average country could lay in a year. And they don’t just do it once. They keep spawning, over and over again, like the Energizer Bunny of the sea.
Yet, with all those eggs, only a few hatchlings make it to adulthood. A baby sunfish starts life as a 2.5 mm larva, smaller than a grain of rice, and must survive a veritable gauntlet of hungry mouths before it balloons into a behemoth. It’s the marine equivalent of a Pokémon evolution on steroids.
No Tail? No Problem
One look at the mola mola, and you’d be forgiven for thinking it’s swimming backwards or halfway through a transformation. Unlike other fish, it lacks a true tail. Instead, its body ends in a strange lumpy structure called a clavus, formed where the dorsal and anal fins meet. This means it flaps through the ocean like a giant, confused bird. Some divers say it’s like watching a flying saucer awkwardly paddling in the sea.
Despite its odd form, the mola mola can dive deep, breach the water like a whale, and occasionally shock the heck out of boaters by popping up without warning. And although it’s not aggressive, it’s been known to accidentally damage boats just by bumping into them, not bad for a fish that looks like it couldn’t hurt a sponge.
Jellyfish Junkies and Cleaner Station Regulars
Mola molas have refined tastes, they primarily feast on jellyfish, salps, and other squishy sea treats. But all that drifting through plankton-rich waters comes at a cost. These giant fish attract parasites like magnets to a fridge, up to 40 different kinds have been found hitching a ride. That’s why mola molas often visit cleaner fish stations, where tiny wrasses and even bold seagulls help pick off the pests.
In fact, they’ve been spotted leaping from the water to try and dislodge parasites, a 2-tonne acrobat hurling itself into the air just to scratch an itch. If that’s not commitment to hygiene, we don’t know what is.
