Ever17 -out of infinity-

Ever17 is the tale of seven individuals who become trapped 51 meters below the surface in the underwater marine theme park 'LeMU'. After an incident, almost half of LeMU becomes flooded, and the path to the surface and the communication lines are cut off. In addition, LeMU is under constant assault by severe water pressure, limiting time to find a means of escape to 119 hours. Escape is not the only concern, however; many questions arise as to the legitimacy of the accident and whether or not those trapped there were brought there for a purpose.

[From Wikipedia]