Tom Swift and His Undersea Search

A Mr. Dixwell Hardley approaches Tom with a proposition to help recover sunken treasure. Mr. Hardley was onboard a ship which was carrying gold to help finance an illegal revolution. When the ship sank, Mr. Hardley overheard the captain recording the coordinates. Now he wants Tom's help to recover the gold, under the guise of both financing the expedition as well as rewarding Tom with a portion of the recovered treasure.