I have been unable to find any decent information online about his topic...I gather that, at least in Europe, it sort of became an accessible means of studying the ocean around the mid-18th century; but surely there must have been substantial curiosity and some attempts made before this?
The greeks free dove for sponges, salvage, even using divers to clear antiwarship obstacles or cut mooring lines or enemy warships. There is a carving from 900 BC that shows a diver using a bladder as a breathing device. This book also describes the use of diving bells and similar technology from the 16th century, primarily for salvage projects. In case the link doesn't work the book is called "Exploring the History of Hyperbaric Chambers, Atmospheric Diving Suits and Manned Submersibles" by Joseph Stewart