Sténuit is one of those remarkable renaissance men that the mid-20th century proved so good at producing: He has been variously an explorer, a historian, a journalist, an author, an archaeologist, a business advisor, an engineer, a dolphin advocate, a treasure hunter, and a spelunker. In 1953, at the age of 20, Sténuit -- who was then studying politics at Brussels' Free University, preparing for a law degree -- read Harry Reiseberg's 600 Milliards Sous les Mers, a fictional account of an undersea treasure hunt.
Sténuit, whose side passions were scuba diving and (because this cannot be said enough) spelunking, was inspired. He promptly dropped out of school, and the next year began searching for the Spanish treasure that might remain from the 1702 Battle of Vigo Bay. Unsuccessful in that attempt, he teamed up with another treasure hunter, the American John Potter, doing search and recovery for the Atlantic Salvage Company.
In 1962, the engineer Edwin Link -- the inventor of the flight simulator -- tapped Sténuit to test the submersible decompression chamber he'd developed to allow for long-term stays underwater. The Link Cylinder was eleven feet tall and three feet wide, designed to be suspended from a surface vessel and submerged vertically. (Its picture at right -- more tin can than pioneering vessel -- suggests the measure of faith Sténuit placed in Link as he climbed inside the cylinder.) On August 28, at Villefranche-sur-Mer on the Mediterranean Sea, Sténuit spent eight hours underwater -- at a depth of 60 feet -- locked inside Link's submersible decompression chamber. He breathed Heliox, a combination of oxygen and helium that had previously been reserved for medical uses.
That submersion, however, was only preparation -- for the longer underwater stay that would give Sténuit his "first aquanaut" status. Starting on September 6, 1962, Sténuit spent over 24 hours on the floor of the sea, submerged in the Link Cylinder -- this time at a depth of 200 feet. Link controlled operations from the surface, aboard his yacht, the Sea Diver. Though a mistral wind caused the cylinder containing Sténuit to rise to the surface prematurely, the pressurized cabin of the vehicle ensured that, despite the early rise, he was spared from decompression sickness.
Sténuit followed up that first Man in Sea experiment with another one, also under Link. This one took place in June 1964 and found Sténuit accompanied by Jon Lindbergh (one of Charles' sons). Link had designed what he termed the SPID (short for Submersible, Portable, Inflatable Dwelling), and the two men lived in that makeshift dwelling for 49 hours, off the coast of the Bahamas, at a depth of 432 feet. They breathed the same helium-oxygen mixture that had sustained Sténuit during his previous two submersions.
After those experiments, in 1965, the Man in Sea project was taken over by Ocean Systems, Inc. Sténuit would go on to act as an advisor, researcher, and development engineer for the company, continuing to do test dives of new underwater habitats himself -- the goal, always, to expand livable environments to greater and greater depths. He would also dabble in deep-sea oil drilling and author 12 books about his undersea adventures. Now nearly 80, Sténuit continues to explore the ocean floor, mining shipwrecks in search of unknown treasures.
Uncaptioned images, top to bottom: Sténuit inside the Link cylinder (via The International Technical Diving Magazine); the Link cylinder itself (via The International Technical Diving Magazine); two of Sténuit's 12 books, including the exquisitely covered The Dolphin, Cousin to Man (via Amazon).