Riptide is a 1998 thriller novel published by Tor Books. The standalone story is the fourth full-length Preston-Child collaboration.
Inspired by the real-life mystery of the Oak Island Money Pit, this novel involves Dr. Malin Hatch, owner of the mysterious Ragged Island. The island, supposedly home to buried pirate treasure, bankrupted his family and resulted in the death of his brother as a young boy. Hatch is approached by a group of "recovery specialists" looking to use advanced technology to recover the treasure.
- Riptide is the only Preston-Child novel to not have any of its characters reappear in another book.
- In The Cabinet of Curiosities, while searching the Central Archives at the museum, Nora Kelly comes across late 19th-century correspondence from a herpetologist from Riptide's fictional town of Stormhaven.