The full origins of the being known as the Merman are shrouded in mystery. Sometime in the 1920’s, a small quasi-piscine infant was found floating on a log in a river by a local farmer.  Thinking him abandoned, he took it home to his wife for safe-keeping and when no one claimed it, raised it as their own.  Giving him the named Jon Rogers, the new parents were struck by their adopted son’s ability to swim.  At two, he swam as well as a much older child and at six, could stay underwater for half an hour, something he did to escape the bullying for his odd fish-like appearance.  As a teen-ager, he followed the river out to the ocean, where he encountered a tiger shark and killed with his bare hands.  When he finally reached    adulthood, he struggled to retain employment as he was constantly off swimming.

One day after being fired from another job, he mused that fish in the wild just take what they need and that he should do likewise.  He started a career of robberies, holding up small grocers and shops, apparently with nothing more than a water gun and escape route of water nearby.  Police repeatedly failed to capture him and he was largely unidentified until a chance meeting at an aquarium in nearby Keystone City.  That day, Jay Garrick and his girlfriend Joan William were escorting her nephew on a tour of the aquarium.  Jon Rogers was also visiting and was drawn into a conversation with the boy until both of them fall into a tank with a large octopus.  As the cephalopod slowly drowns them, Garrick switched to his identity as the Flash and frees Joan’s nephew.  When he returned for Rogers, he found the Merman waiting patiently beneath the surface.    Surprised at his resilience, Garrick liberated him from the tentacles of the octopus and bade him farewell.

When the Flash returned to Joan and her nephew to her apartment, they found the sheriff of Rogers’ hometown waiting in the lobby with Mrs. Rogers.   There, they explained their dilemma – a mother’s concern for her wayward son, the sheriff’s frustration with his failure to catch him.  The Flash agrees to help but in the meantime, the Merman has expanded his operations to a larger gang.  To facilitate his water-based crime spree, he instructs his gang to blow up the Morris Dam and flood his hometown.  Radios in Keystone light up with new of the disaster and the Flash races to save as many as he can.  As he finishes, he spies the Merman with large money bag making an escape.  He dives in after him but in the murky water, loses his quarry.  The Merman returns to his gang but Flash gets their first and makes short work of them.  Frustrated with his useless lackeys, the Merman takes what money he can and heads out to sea. 

Alone  in the depths, the Merman begins to pine for human contact.  He finds treasure beneath the sea in the form of gold and other valuables and ponders a way to turn them into useable currency.  His reveries are interrupted by the sound of boat engines, a passing yacht on which Jay and Joan are currently enjoying an evening cruise.  Slipping aboard, the Merman tries to scuttle the ship and seize its cash but the Flash catches him.  After a brief melee, the Merman leaps overboard and Flash gives chase but loses him in the dark water.  As the Flash returns to the boat, the gloating Merman is caught in a cable which tangles itself around his neck.  As the Merman begin to drown, the yacht goes on his way, it’s assailant presumed drowned beneath the waves (Flash Comics #58).

Whether the Merman actually drowned, what he was and where he originally came from have yet to be revealed.