One of the few games to take advantage of the Dreamcast's date monitoring function, Seaman is essentially a blend of a Tamagotchi and the After Dark "Fish" screensaver, with the added feature of the creature sassing the player.
The game's story tells of an ancient Egyptian legend about a creature that is half-man, half-fish. It then jumps to the modern era, claiming that in April 1932 a French scientist named Jean Paul Gassé discovered the bones of a Seaman, and in December of that year came across a live one in the catch of some fishermen near Alexandria. The story continues in astonishingly elaborate detail up to the present-day. Players of the game are assistants in Professor Gassé's laboratory, attempting to raise Seamen from birth to maturity. The narrator, none other than Leonard Nimoy, helps the player by starting each session with an explanation of the previous day's events, the current status of the tank, and what might happen in the upcoming day. Leonard also notices if the player usually shows up at the same time each day (and will call him or her a creature of habit) or checks in multiple times a day (he'll say it is not necessary to visit Seaman so often - in other words, "you're a loser, Player One").
Players must control the air, temperature, and food for the Seamen. These are all fairly simple tasks, as the creature usually complains if something is amiss. More difficult, though, is keeping the Seaman happy and teaching it to speak.
The game's other attractive feature is the speech recognition unit. Each game is bundled with a small microphone that plugs into the Dreamcast controller, and a series of commands and phrases can be spoken into the microphone and actually understood by the game. Players may try to ask the Seaman questions, but it's considerably easier to answer its getting-to-know-you inquiries, which are stored in a VMU and recalled in further conversation. It frequently uses the player's responses as opportunities to tease the player, and will make special comments for holidays and unique dates. While it is possible to abuse the Seaman for such comments - it doesn't like to be picked up or flicked - it is probably wiser to let them pass. A bit of punishment won't hurt, though, as Seamen are very ticklish and despite protesting will actually grow happier if you tickle them.
It should probably be noted that Seaman can get quite rude. Young children might not appreciate the references to sex, politics, and religion.
Resources and Further Information:
http://www.yoot.com/ - Official site for the game, mostly focused on the detailed story behind Seaman.
http://www.sega.com/games/post_gamegame.jhtml?PRODID=194 - Sega's page for the game.
http://www.gamefaqs.com/console/dreamcast/game/24507.html - FAQs, guides, and in-depth details.