Atlantis is a prototype for a game based on the Disney film of the same name, that was created by Ubisoft Canada in 2000 / 2001. As we can read on Wikipedia, the movie begins with a reenactment of the sinking of the legendary city of Atlantis, but the main story begins thousands of years later in 1914, when Milo James Thatch, an aspiring young cartographer/linguist/explorer, believes he has found the secret to the location of Atlantis.
While some Atlantis games were released for the GBA, PSX and PC, a PS2 version was never published. It seems that Ubisoft tried to pitch their demo to Disney, but for some reasons they decided to not give the permission to use the Atlantis license for a Playstation 2 project.
Thanks a lot to Stephane for his help in preserving some screens from the prototype!