John Finnegan operates a small smuggling vessel in the South China Sea with his crew, including the anxious mechanic Joey Pantucci, until their client Hanover fires a torpedo that cripples their ship and strands them at sea. The damaged vessel drifts near the luxury cruise liner Argonautica, where Finnegan encounters Trillian St. James, a thief who escaped by jet ski after stealing from the ship's owner, Simon Canton. Hanover returns with armed mercenaries led by Mulligan and Mason, forcing Finnegan at gunpoint to guide them onto the abandoned liner in search of hidden wealth. Once aboard, the group discovers signs of sudden panic and partially consumed remains, then witnesses tentacles emerging from submerged sections to snatch victims toward a digestive core, forcing a shrinking band of survivors toward a desperate escape plan involving stored explosives.