Reading the Water
by E.R. Cross
The study of the seas, lakes, rivers and other bodies of water is the science of hydrography. It is not necessary for divers to be hydrographers. However, for maximum safety and the greatest enjoyment, a good working knowledge about some aspects of the diving environment is helpful. With a combination of knowledge, experience and observation, enough can be learned of the secrets of areas so that diving is not only safe and enjoyable but rewarding. I call getting this information reading the water. Whether it is an ocean, a lake or a river, reading the water is a skill that will improve the safety of a dive. Water conditions should never exceed the experience of the least qualified diver.
This Technifacts will discuss the effect wind has on water. Other conditions involved with reading dive waters will be reviewed in the future.
Physically, both air and water are fluids. Both flow relatively easily and are almost constantly in motion. Surface waves, surge and currents are forms of water in motion. These conditions are variable owing to external forces. Wind is air in motion. It has characteristics comparable to water in motion. The direction and force of the wind are similar to currents; gusts are similar to surge. Bodies of water have a relatively small effect on the wind. Conversely, wind has tremendous impact on water. The impact of wind on water can cause more problems for dive safety than almost any other external force.
When reading the water divers must be aware of several related things. Wind blowing with a current may increase the speed and depth at which the current flows. Waves in such an area will probably decrease in height and increase in length. Wind blowing against a current will probably decrease the length of the waves and increase their height, making them more dangerous. An offshore wind will cause a short, sometimes violent chop to develop on the incoming waves (swells). This condition may be difficult to cope with when trying to return to shore or a boat. An onshore wind may flatten and increase the length of incoming waves, making them easier to cope with on returning from a shore dive.
When there is a large land mass near a large body of water, the wind may be calm or blow offshore with less force in the mornings and get stronger, blowing toward the land mass, in the afternoons. This is because the air over the land will heat up and start to rise during the day. The cooler air over the water will then flow toward the land. The winds force may be related to the difference in the air temperature over the land and water. Late afternoon winds may become almost gale force in many coastal areas.
Many early civilizations revered the sea as the mother ocean. Learn what mother ocean can tell you about your dive waters by reading the water.
Many divers are underwater hunters, including some who make study collections of marine life such as shells, coral and fish. Diver Jeff Bargeski collects shells for research. He recently reminded me researchers collect only in areas of abundance and then selectively. Collectors/researchers make their duplicate specimens available to others having similar interests. This reduces potential impact on the environment. Jeff recently completed his study on shells in the volute family. Anyone interested in the shells may write to him at 368 Carnegie Boulevard, Holbrook, NY 11741.
Several SKIN DIVER readers have asked me for published sources about the location of two wrecks. One of these vessels is real, the other is a legendary vessel that never actually became a wreck.
The real wreck is the MS Diamond Knot, sunk off Crescent Bay on the U.S. side of the Strait of Juan de Fuca a few miles west of Port Angeles, Washington. The Knot sank as a result of a collision with the vessel Fenn Victory on August 13, 1947. She rests on her port side in 135 feet of water, with about 80 feet over her starboard side. Most of her cargo of canned salmon, valued at $3,500,000, was successfully salvaged.
Firemans Fund Insurance Company, with head offices in San Francisco, California, was the principal insurer. Firemans Fund published a factual account of the sinking and salvage of the cargo. This 30 page booklet is entitled The Story of the Diamond Knot.
The dramatic 1947 salvage of the cargo of the Diamond Knot was also filmed in 16mm color with technically accurate narration. The U/W portions of the film were presented by scientifically correct animated drawings. Copies of the film and of the 30 page booklet may again become available.
THE WRECK THAT ISNT
Many people believe the Mary Celeste was wrecked. Such is not the case. The celebrated story of the Mary Celeste began on November 5, 1872. It became a notable mystery on December 4, 1872, when the De Gratia found the Mary Celeste adrift in the Atlantic. Her crew and passengers had deserted her without a trace. The Mary Celeste was towed into port and eventually put back in service.
Of the five insurance companies that insured the vessel and her cargo, only one remains, the Atlantic Mutual Insurance Company of New York. They had written Insurance on Freight on Charter. On the 100th anniversary of the company, in 1942, they published a 14 page booklet titled The Mary Celeste; The Odyssey of an Abandoned Ship. Possibly this small booklet may also become available.
Readers are invited to send a stamped, self-addressed envelope to E. R. Cross, c/o Technifacts, SKIN DIVER Magazine, 6420 Wilshire Boulevard, Los Angeles, California 90048-5515 with a request for information on both the Diamond Knot and the Mary Celeste.
There are more than one million wrecks in the waters of the world. In future issues of Technifacts many of the major wrecks will be reviewed. Stay with us and become one of the worlds best wreck divers;from your armchair. Take care and when you do dive, dive safely.