The man named Kingsley Rice is a native to Earth-712 and a founding member of the Squadron Supreme. Joining the team to preserve the natural balance of man's world with the Oceans and due to his natural mutant powers to survive in deep waters and communicate with sea animals he took the identity of Amphibian. After fighting crime alongside the Squadron for sometime they would face the other dimensional entity known as the Overmind, who took psionic control of the Squadron and most of the worlds government. Amphibian and the Squadron would be pitted in battle against the Defenders from our Earth. The Defenders defeated the Squadron and freed them from the Overmind's control. The Squadron would realize the stark reality of the damage that they had done to their world and that they were now left having to clean up the mess.
As the Squadron attempted to develop a new form of government to resolve from ever going though the same horrible situation again they developed the Utopian Project. After believing that the Power Princess's former life on Utopia Island proved to be the best example of the future of society on their Earth the teams alliances started to change. Amphibian felt that the behavior modification machines created by Tom Thumb were against the natural balance of mankind and believed that their use was innately wrong. Objecting with a few other members against the use of the machines he was voted down by the majority of the team who agreed in seeing its use go through. After seeing former super criminals and adversaries behavior modified, Amphibian decided to take matters into his own hands. Going to Tom Thumbs lab he destroyed every Behavior Modification machine that he found. He then left the group over their controversial Utopia Project, which he saw as super-humans taking over the world for the "greater good".
When the Squadron had been stuck on the Avenger's home dimension of Earth while combining forces with the cosmic hero named Quasar, they came home to a revolutionized world with warrants out for any Squadron member found. The few members left then had the task of reuniting all of the surviving founders of the Squadron.The Power Princess went looking for Amphibian and convinced him to return to the surface world and help his former teammates in bringing freedom to the world, as she had seen the ill of her Utopian Project. Amphibian came back to Utopia Island with Power Princess where he then rejoined the Squadron. Amphibian fought alongside the Squadron to attack the current evil government, the Global Directorate and succeeded in toppling its reign.
Amphibian's mutant powers allow his body to adapt to undersea conditions; the deeper he swims, the more fish like his metabolism and physiology become. He is a powerful swimmer and can swim to inhuman speeds, and depths. He also has superhuman strength and was once seen overturning a tank with the aid of Power Princess. His huge amounts of stamina increase the deeper he swims underwater. He also has the ability to communicate with ocean mammals and keeps company with Dolphins.
The daughter of "Phil" and "Debbie," not much is known about the second Amphibian, or Kingsley as Dr. Spectrum calls her. When Debbie was pregnant with Amphibian, she and Phil were driving, probably to the hospital as they had to pull over suddenly and Debbie had the baby then and there. Phil and Debbie both snapped when they saw it, and Phil took off running, while Debbie waded out into the nearby ocean, and tried to drown herself and the baby. Amphibian swam off and wasn't heard from or seen again for a long time.
When she met some divers, they freaked out as well. A picture of Amphibian carrying one of the dead divers ashore was taken, and the camera eventually found. It looked as though Amphibian had intentionally tried to kill the divers, and was taken as such until Joe Ledger/ Dr. Spectrum befriended her when the crystal had taken him underwater to recuperate from a fight with Hyperion. It was his vouching for her that got the government to clear up the bad PR, and bring her aboard the Squadron Supreme. It's presumed the mutation was caused by the nano-virus released from Hyperion's space ship when it first came to Earth.