Abstract: A vivarium comprising at least one terrarium completely submerged in the water in an aquarium. The terrarium and the aquarium shares a common bottom, but are not in fluid communication. The terrarium is accessible through an access opening on the bottom of the terrarium. There can be transparent passageways linking various portions of the terrarium and extending through the aquarium, for travel by animals kept in the terrarium. There can also be transparent passageways linking various portions of the aquarium and extending through the terrarium, for travel by the marine organisms kept in the aquarium.