Books like Night probe! by Clive Cussler

In the midst of an international crisis, naval commander Heidi Milligan stumbles upon a reference to a long‑buried North American Treaty—a secret pact that could deliver energy and economic relief to an ailing United States. The treaty’s two copies were lost at sea in separate incidents centuries ago, and finding them now is crucial for the nation’s survival. The President sees the treaty as the nation’s only hope, but a British counterplot—led by agent Brian Shaw—aims to prevent its implementation. Shaw, an experienced spy who has often partnered with Americans, now faces his most dangerous mission: stop Pitt and Milligan from retrieving the key documents. Dirk Pitt, famed for his daring rescue operations, is tasked with retrieving the treaty while navigating a battle against Shaw and facing a tense love triangle. With the world’s future hanging in the balance, Pitt races toward an underwater showdown that tests his limits in "Night Probe!"

First publish date: 1981