Prior to the establishment of the Deep Sea Diving School at the Washington Navy Yard in 1928, divers were trained by more or less hit or miss methods. Gunner’s mates and torpedomen were given a very short period of instruction in diving incidental to schooling in their rates, but only a few men, who became fond of diving and were well qualified physically and mentally for the work, proved to be valuable in this field. Now the course instruction at the school is six months in length. The students concentrate on actual diving and the study of diving gear and diving problems, so that when they leave the school they are specialists and well qualified for all kinds of diving activities.
The training of officers had been so neglected that only a few qualified divers were available for actual inspection dives during the salvaging of S-51 and S-4. It will be more in keeping with service traditions if in the future officers lead the way in diving as in all other lines of naval work.
Candidates for entry into the school are required to pass very strict physical examinations in order to minimize the number of accidents caused by caisson disease.* The condition of the heart and lungs is especially important because decompression tables are based upon normal functioning of those organs. Excessively fat men are barred because the fatty tissue in the body absorbs five times the amount of nitrogen gas as the other tissues. However, the normal, healthy individual has little to fear from the effects of high air pressures, provided the approved methods of decompression are followed, although danger is always present. Having passed the required physical examination aboard ship and the check by the doctor assigned to the school, the student diver is ready to start his course of training.
An indoor tank is used for training and instruction purposes. The divers enter through a hatch at the top which is closed during pressure dives. The tank is fitted so that an air pressure may be put into the tank over the column of water to effect hydrostatic conditions similar to any depth of water. When the air pressure is reduced, the effect on the diver is the same as though he were rising to the surface from the bottom and this release in pressure is regulated so that the required decompression is given after each pressure dive. A recompression chamber is used to test the student' diver’s reaction to air pressures and for the treatment of caisson disease. There are two torpedo air compressors and several air banks together with the other incidental equipment necessary in the training work. A 70-foot, especially equipped diving boat is permanently attached to tie school. It is used for all diving performed both away from the school and in the river at the yard.
The student divers are first instructed in the fundamentals of diving, such as operating the air supply and exhaust valves- clearing the ears under an increase of air pressure by yawning and swallowing They are tested for their ability to do this under a few pounds’ pressure in recompression chamber. They are then ready for a dive in the tank under no excess pressure. During these first dives they practice balancing, i.e., adjusting the supply and exhaust of air until they are light and buoyant and float off the bottom or until they are heavy and can lie down and crawl about the bottom of the tank. The first dive is a sensation comparable to any new experience—a first airplane ride, a first train ride, etc., except that you are your own pilot or engineer from the start.
After several preliminary dives, the students handle small tools in the tank. Rivets are cut out of steel plates with hammers and cold chisels, each diver cutting out one before he is allowed to come up. Then two divers are paired. One swings a heavy sledge while the other holds the chisel until another tough rivet is removed. Next each diver cuts a piece of metal with a hacksaw, and after that each diver is required to caulk a seam or a rivet. With an air drill holes are cut in steel plates, and the holes are then tapped. During all this work the divers wear suits with gloves attached to accustom them to working under the hardest conditions. It is no easy task to replace a broken blade in a hacksaw while wearing the heavy 3-fingered diving gloves. The aims in view during this phase of the training period are twofold: to train the diver to work under water, and to accustom him so thoroughly to working in a diving suit that he will gradually take his mind off the fact that he is in a diving suit and his reactions to the adjustments of his air supply and the other movements made necessary by the suit will become more or less automatic.
The students, having become proficient in the use of hand and power tools in the tank, are next required to dive off the diving boat into the river at the navy yard. They are first taught to circle and recover objects from the bottom; then, they are required to perform the same work in the muddy blackness of the river as they did in the well-lighted tank. This phase of the training is important lest the student think himself an expert without meeting the most adverse visibility conditions which he will encounter in the service.
Some time during each class the school is called upon to do diving by someone in difficulty. Once it was to help clear away wreckage consisting of passenger train cars and a steel trestle that had fallen into the Eastern Branch of the Anacostia River, which was obstructing the main line of the Pennsylvania Railroad. Another time the class recovered a body drowned in the Chesapeake and Ohio Canal. Once they searched unsuccessfully for a safe which bank robbers were reported to have dropped into the Potomac River. The last class salvaged two sunken boats, one for the Naval Air Station and the other a racing boat that had turned over and sunk during the Gold Cup Race. Such diving gives the students practical experience in practicing their new-found art.
The students dive to increasing depths to 90 feet and are then designated divers second class and draw extra pay of $10 per month in accordance with the Bureau of Navigation Manual. The divers are now taught to burn steel under water in the tank, using the hydrogen-oxygen underwater cutting torch. They were required to use the torch in the river after becoming proficient in its use in the tank. Immediately after the gas torch training, the use of the electric arc under-water cutting torch is taught, but, being immovable, it is not used in the river.
The classroom work consists of a study of the Diving Manual, keeping a log on diving details, the calculation of air supply problems, practical work in repairing and mending diving suits, breaking down and overhauling diving hand pumps and testing them for efficiency. The students dive with the shallow-water diving outfit and are required to make several escapes from increasing depths in the tank, using the submarine escape apparatus (lung).
Dives are then made in the tank at each 25-foot depth from 100 to 300 feet. Before each of these deep dives, the student is given a physical examination and is subjected to the equivalent air pressure in the recompression chamber to test his ability to withstand the air pressure. Besides the ever-present danger of caisson disease, another difficulty is experienced starting at a depth of 250 feet. At that depth or the equivalent pressure of 110 pounds per square inch, the oxygen pressure* in the air is the same as breathing pure oxygen at 1.5 atmospheres gage. The oxygen pressure begins to have a narcotic effect, causing the diver to feel a trifle “queer.” Long exposures at depths in excess of 250 feet would result in oxygen poisoning, a form of pneumonia. For this reason, very deep dives have been limited to a maximum of 15 minutes.
For the past three years a submarine has been assigned to the school each summer for two periods of three weeks each, one period for each of the semiannual classes. During this important training period, the class is taken aboard the diving boat and proceeds with the submarine to the Dahlgren-Piney Point area in the Potomac River. The submarine anchors in about 75 feet of water each forenoon, makes a stationary dive, and lies on the bottom for 3 hours. Large wooden buoys with bow, stern, descending, and telephone lines attached have been placed aboard the submarine so they will float to the surface as she sinks. These buoys are picked up by the diving boat which moors over the submarine ready for diving operations. Frequently, the buoys or the lines foul and the divers gain valuable experience in clearing them. Each diver makes a descent each day if time permits. He first familiarizes himself with the deck of the submarine, then he locates the various salvage air-line connections, and finally he attaches an air line to one of them. During one of his dives he goes to the conning tower or to one of the deck hatches, makes metallic contact with the submarine hull with his helmet, cuts down his air supply somewhat to avoid interference from air noises, and converses with the men inside the submarine.
During the time aboard the diving boat and operating in the Potomac, dives are again made in the mud and current to train the students to make their way along the bottom, if possible, under adverse tidal conditions so that the school will send to the service something more than tank divers.
The successful students are finally designated as divers first class and are sent from the school to submarine rescue vessels or to submarine tenders where they must make 4 dives to a depth of at least 150 feet for a minimum of 20 minutes every 6 months to remain qualified as divers first class. Officers detailed to command submarine rescue vessels or to duty at lung training tanks, and warrant officers detailed as diving supervisors have taken the full course at the school, undergoing exactly the same training as the enlisted men, with additional emphasis on the methods of treating caisson disease, the use of decompression tables, and the theory upon which the tables are based This expert training of officers is necessary’ to provide the service with trained diving supervisors so that the number of accidents in diving may be reduced to a minimum
* Caisson disease or compressed air illness, known popularly as the “bends,” is a disease from which divers and other compressed-air workers suffer because of the liberation of bubbles of nitrogen gas in the body on decompression or the release of the pressure. Symptoms vary widely. Skin rash indicates a mild release of bubbles; pains may occur in joints, muscles or any part of the body; paralysis of the extremities, dizziness, difficulty in breathing, and loss of consciousness may occur in extreme cases.
* Air contains roughly 20 per cent oxygen; therefore, if air is compressed to 5 atmospheres absolute, the oxygen pressure in the compressed air is equal to pure oxygen at atmospheric pressure. Similarly, if air is compressed to 10 atmospheres absolute, the partial oxygen pressure is equal to pure oxygen at 2 atmospheric absolute.