Michael Hawk was an investigative reporter with access to a criminal fortune who appeared in appeared in 14 books published during 1980-81. I can only assume author Dan Streib didn't need to eat or sleep! The final book in the series was called The Treasure Divers but didn't feature any diving action on the cover. Book three, The Power Barons, did however. Thanks to Chris for the cover scan. (Click for larger image).
Long time Art of Diving followers might find the girl on the cover looks familiar.