Additionally, a PC spin-off called SeaMail was released for Microsoft Windows, with the Seaman being able to interact with the user's applications from the desktop.

The mechanic operates in real time, so the player is required to check on the Seaman every real-time day or he could die.

Over the course of the game, the player is required to evolve their Seaman to different stages in its life cycle, eventually transforming into a frog-like creature outlined on the disc's cover.

The Seaman begins its first days of life as a Mushroomer, a form which consists of a well-developed optic organ and a flagellum.

After emerging from the deceased body of the nautilus, the organism enters a stage called the Gillman, which resembles a cyprinid fish with a human face and a tentacle-like tube atop its forehead.

During this stage, the Seaman becomes capable of speech but can only communicate in gibberish by reiterating comments made through microphone input.

Shortly after depositing the eggs, the female also dies, leaving the player a new generation of Seamen in a new evolutionary stage.

It is an amphibious creature resembling a frog and like the Gillman, it has a human face and a tentacle-like tube atop its forehead.

While anything concerning metamorphosis and reproduction is left to speculation while the Frogmen are in the wild, it can be assumed the Seaman will eventually lay Mushroomer eggs and start the cycle over.

As a new pet owner, the player is given the responsibility of caring for and learning about the enigmatic "Seaman" species using a replica of the discoverer's laboratory.

Leading academics, however, dismissed him and his work as a PR stunt, leveraging the complaint against him that he lacked the proper evidence to support these outlandish findings.

In 1997, the ABARI announced there was a strong possibility that these Seaman species were closely related to the origins of ancient civilizations in Egypt.

On February 15, 1999, parts of Gassé's journal and note entries were found in the Masuda family storehouse in the city of Matsusaka in Mie Prefecture, Japan.

Professor Kendare Takahashi, who was directing the Japanese branch of the ABARI, successfully managed to breed Seaman eggs in captivity in July the same year.

During development, Sega had requested that a celebrity be used if possible, but Saito was hesitant, but later said that the fact that he played the role himself was "the key to success" because it gave him the advantage of being able to rerecord lines as many times as he wanted, so it was no longer a question of money.

It was conceived and designed by Saito, who originally came up with the concept of a joke when one of his coworkers was creating a tropical fish simulator.

The decision to develop the game for the Dreamcast was made when he was introduced to the vice president of Sega, Shoichiro Irimajiri, who thought it could make the console a market leader.

The prototype was initially developed on a Macintosh computer, with a year-and-a-half spent on converting it into a Dreamcast game.

To fix the issue, Yoot Saito changed the phrasing to say, "You talk too long, I don't understand" in order to inform players they need to use shorter and simpler sentences to interact with the Seaman creature.

[12] Localization was handled by Sega of America and spent a total of nine months, where multiple changes to comments were made regarding sex, politics, and slang based on cultural differences.

[13] A limited-edition demo version titled Christmas Seaman was released in Japan on December 16, 1999, and available for only ten days either through the Sega Direct online store or as part of an exclusive red Dreamcast pack-in.