Night Probe!

Dirk Pitt proved invincible in Raise the Titanic! Now, with the future of virtually every person in the world at stake, he is enlisted to spearhead his most daring mission yet—the rescue of a vital document for the United States. To an energy-starved, economically devastated America, possession of this document is worth billions. But to Great Britain, it’s worth a war. Pitt’s quest plunges him into a head-to-head confrontation with Britian’s most cunning secret agent—and into the throes of a torrid love triangle. As time runs out for a desperate America, Dirk Pitt races toward an underwater clash more terrifying than anything Clive Cussler has ever created—the breathtaking climax of Night Probe!
In May 1914, both copies of a secret treaty between the USA and Great Britain are apparently lost forever. It promised a huge sum of money to Great Britain, to be paid during World War I, with Canada to be given up to the US in return after the war. Dirk Pitt is sent to retrieve the treaty.