The Maracot Deep, by Sir Arthur Conan Doyle. Part I.

Professor Maracot, accompanied by two American associates, conducts an exploration of the Atlantic Ocean floor, beginning in a diving bell of his invention. The results exceed the underwater thrills we may recall from Sea Hunt and Jacques Cousteau. 

Maracot, a contrastive successor to Professor Challenger, whom Edgar Rice Burrows had borrowed from Doyle, leads his colleagues into unanticipated adventures that rival those of Burrows's Barsoom novels. These climax with a supernatural contest of wills.