While On A Dig In A Romanian Forest, A Group Of Scientists Make A Startling Find. Dating Back To The 13th Century, They Find A Huge Abbey, Which Was Built Over The Entrance To A Massive Network Of Subterranean Caves. Eager To Learn What Lies Within The Caves, The Scientists Discover To Their Peril That A Large Part Of The Cave System Is Under Water. The Scientists Hire A Team Of American Spelunkers Who Are Trained In Exploring Underwater Caves. The Team Is Led By Brothers Jack And Tyler. Armed With New High-tech Scuba Gear, Jack, Tyler, And The Rest Of Their Crew Dive In To Investigate The Caves. A Mishap Traps Them In A Cavern Beneath The Surface, And They Soon Discover They Are Not Alone.