The Ocean, specifically under its surface, is one of the most hostile habitats on earth to humans. The average person can only hold their breath between 30-90 seconds, but despite this inherent danger we have been drawn to the ocean throughout history. Over the past few thousand years, humans have been inventing devices that would allow them to explore beneath the waves for longer periods of time. One of the oldest recorded instances of humans using external devices to aid in diving comes from Aristotle, who described the use of a diving bell in the 4th century BCE. Diving bells functioned by capturing air on the surface and when submerged it would create a temporary air pocket, allowing the diver to breathe. The diving bell remained the primary mode by which divers received air while underwater until the 1600s when the first air pump was invented. These pumps were used to provide divers with a continuous supply of oxygen from the surface. However, under this system the depth and movement of divers was limited by the length of the air hose. This challenge was overcome by the early 1900s when inventors were able to produce the first functional self-contained diving system. While this was a tremendous advancement in the world of diving it was not until the 1940s when modern diving began to take shape. In 1943, Jacques Cousteau and Emile Gagnan patented the aqualung, the design for which most modern SCUBA systems are based on. The invention of the aqualung paved the way for advances in underwater exploration, scientific diving, and recreational diving too.
Every year around 1 million people become newly certified scuba divers and have a whole new world open up to them. Recreational divers can spend their time exploring reefs, shipwrecks, and exotic locations all while seeing some of the planet’s most amazing creatures. However, diving is not solely for recreation. Scientific divers are divers who use their expertise to study underwater environments through the use of scuba or other specialized equipment. The main role of these divers is to gather data and make observations about the underwater environment. Fascinating discoveries related to biology, geology, anthropology, and chemistry were made due to the hard work of scientific divers. While diving is incredibly beneficial both recreationally and scientifically, divers face unique challenges that may not be present in other hobbies or scientific studies. Three major challenges are related to maintaining body temperature, ability to to breathe, and controlling buoyancy.
In order to keep warm and maintain the proper body temperature while underwater, divers need to wear some sort of insulating suit. During the early years of diving, around the mid-1800s and into the 1900s, divers wore water tight canvas suits with either a helmet or mask made of copper. While these suits provided adequate insulation they were heavy and cumbersome to move in. By the late 1800s and into the 20th century, dive suit manufacturers constructed suits that consisted of a solid piece of rubber, sandwiched between two layers of twill canvas. Rubber seals where fitted to the wrist and neck holes to make the suit waterproof. These canvas suits usually had a very baggy fit, allowing the diver to wear clothing under the suit to help keep warm. Suits like these are occasionally used today but it is often done for educational or demonstration purposes. Over the last 70 years significant advancements have been made in the design and construction of diving attire making this style obsolete.
Modern divers wear one of two insulating suits. The first and most common diving attire is called a wet suit. The first modern wet suit was constructed in 1952 out of neoprene, a type of synthetic rubber. These suits function by trapping a thin layer of water between the diver and wetsuit. Over time the diver’s body heats the water until it reaches body temperature. To ensure the water trapped in the suit does not lose heat to the water surrounding the diver, tiny trapped bubbles of gas in the suit act as thermal insulation. Much advancement has been made to the wet suit since its invention including the use of new materials, increasing thickness, and better construction techniques. However, the way wet suits function remains the same. The second type of suit that modern divers use is a dry suit. Modern dry suits are similar to historical suits in they both provide insulation through the exclusion of water. In contrast to wet suits, which trap a thin layer of water in the suit, dry suits have water tight seals around the neck, wrists, and ankles to keep water from leaking in. Typically a dry suit protects the diver’s body except the head, hands, and possibly feet. However, there are suit configurations that protect those areas as well. These suits will keep a diver warmer than a wet suit because the air trapped in the dry suit is a better insulator than the water and gas bubbles in the wet suit. Furthermore, you can wear additional undergarments in a dry suit, like a fleece sweater, to provide further insulation.
While wet and dry suits keep divers warm, they still need to be able to breathe underwater. Breathing apparatus have improved dramatically throughout the history of diving. In the early days of diving, divers had to rely on a manually operated pump at the surface to provide them with air. Air would be pumped down to the diver through a leather hose which was attached to the helmet. The helmet was designed with a valve to prevent air flowing out of the helmet in case the hose was cut. Over time advancements were made in the method air was supplied to the diver. The invention of the powered compressor allowed air to be automatically pumped to the diver without having to rely on other people. While advancements were made in surface-supplied air diving, mobility was reduced due to the air hose, and there was the constant risk of it being cut and the diver losing their air supply.
In contrast, modern divers typically use self-contained systems that provide them greater mobility when working or exploring. The average recreational diver breathes either compressed air or an oxygen enriched gas called Nitrox. These gases are contained in an aluminum or steel cylinder that is carried on the back of the diver. The first air tanks used what is known as a J valve. A J valve is a reserve mechanism that was built into the tanks. When the pressure in the tank fell to 500 psi the valve would close off airflow, alerting the diver that they were low on air. The diver would then open the reserve valve by pulling on a rod attached to the reserve lever. These tanks are no longer recommended because there are now reliable pressure gauges available – in addition to the dangers of having a divers air shut off. Modern tanks use a K valve which is more safe and simpler than the J valve. A modern aluminum tank holds about 80 cubic feet of air at 3,000 pounds per square inch. At this pressure a diver cannot breathe directly from the tank because it would damage their lungs.
Therefore, divers use a regulator to reduce the air pressure and provide air on demand (i.e. only when inhaling). Together, a full aluminum cylinder and regulator weighs about 40 pounds. When combined with the weight of other equipment, divers carry between 60-75 pounds of equipment. While the apparent weight of this equipment is dramatically reduced when in water, divers still need to be able to control their buoyancy while underwater.
Buoyancy control is one of the most important skills a diver can have, as it is one of the most efficient ways to control depth during a dive. In the early years of diving, beginning in the 1800s, divers used their helmet, shoes, and weight belts to control their buoyancy. During this time divers would typically ensure that they were weighted to be negatively buoyant in the water. Divers would weight themselves so they could work from an upright position. Divers were so heavily weighed down that a ladder or lift was often used to get them to the proper depth. When at the proper depth, pressure and buoyancy was maintained by pumping air directly into the suit. While this system allowed divers to work at depths of over 100 feet, a malfunction in the pump could cause the diver to ascend uncontrollably which could lead to decompression illness or a suit rupture.
In modern scuba diving, divers use a piece of equipment known as a BCD (buoyancy control device) as well as lead weights to control buoyancy. The BCD is a vest worn by the diver that functions by inflating or deflating a rubber bladder contained within the vest. Instead of holding the diver in an upright position, the BCD and the positions of the weights in it allow the diver to maintain a horizontal position. This is a more energy efficient position and more environmentally friendly because it does not damage the surroundings. By making small adjustments to the amount of air in the BCD, a diver can maintain proper buoyancy throughout their dive. It is important for a diver to monitor their buoyancy because it is affected by their depth and the surrounding water pressure. The deeper a diver goes the greater the water pressure becomes. As water pressure increases, the air in the diver’s tank and BCD is compressed making them less buoyant. To compensate for this, the diver adds air to the BCD until they are neutrally buoyant. When the diver begins to ascend, the compressed air will expand and make the diver more buoyant. In order to perform a safe and proper ascent the diver has to release air from the BCD. This will help ensure that the diver is able to keep themselves from ascending to the surface uncontrolled. Dives are filled with these micro adjustments and it is critical for the diver to understand how the principle of buoyancy functions, and how it relates to them, in order to have a safe and enjoyable dive.
While there is a lot to learn before becoming a certified diver, it opens up a whole new world of exploration. Humans have had a deep connection to water and the oceans for many thousands of years. However, it has not been until relatively recently that humans had the ability to sink below the waves to explore a world filled with fascinating creatures and sites.
· Freudenrich, C. (2001). How Scuba Works. How Stuff Works. https://adventure.howstuffworks.com/outdoor-activities/water-sports/scuba.htm
· Dive Training Authors. (2002). A Brief History of Diving: Free Divers, Bells, and Helmets. Dive Training. https://dtmag.com/thelibrary/a-brief-history-of-diving-free-divers-bells-and-helmets/
· A Basic Guide to Scuba Diving Equipment for Beginners. PADI. https://blog.padi.com/2019/01/14/a-basic-guide-to-scuba-diving-equipment-for-beginners/
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Author: Andrew Pressly, Education and Engagement Coordinator at FMM