The program concept was developed by "Terebi Doga", (a.k.a. Japan Tele-Cartoons or JTC), in Japan in 1965, originally known as "Dolphin Prince" (ドルフィン王子 - "Dorufin Ôji"). Produced as a short experimental trial series of only three episodes and filmed in black and white, "Dolphin Prince" aired on Fuji TV on Sundays at 7:30 pm between 4 April and 18 April 1965. The episodes featured young Dolphin Prince, his mermaid friend Neptuna and Dr. Mariner, with stories entitled "Secret Of The Red Vortex", "Call Of The Sea" and "Attack Of The Sea-Star People". It was a well-received experiment and Terebi Doga prepared to produce a full series follow-up, although this time they decided that their program would be produced in color in order to maximise the potential of the production, both artistically and commercially.