The sea-inspiration to the poet and writer, challenge to the scientist, battleground of militarists, adventureland of sportsmen-continues as one of the last great frontiers for man to conquer. The sea has taken on new meaning as a military medium, with the introduction of nuclear-powered submarines as launchers of guided missiles. The development of new underwater detection mechanisms has brought the importance of marine organisms and their sounds into sharp focus. The detonation of thermonuclear weapons and the dumping of radioactive materials has brought man into a new and more intricate relationship with ocean currents, and with the flora and fauna of the sea. The minute phytoplankton of the sea, formerly of interest only to the bespectacled academician, threatens to invade the domain of the politician in the new era of radioactive uptake. The rapid expansion in human population, presently on an upward spiral of more than 43,000,000 additional persons each year, demands that the nutritionist reexamine man's protein larder. The Food and Agriculture Organization of the United Nations officially has declared that fisheries' products must be increased by nearly 90 per cent if we are adequately to feed the world's future population. In the quest for new chemical agents, pharmacologists and chemists are beginning to turn their attention to the vast untapped resources of the sea. Even the sportsman has turned to the underwater world with renewed interest and vigor. Yes, the ocean is becoming of increasing importance to the health and welfare of mankind. However, with the greater effort to penetrate the ocean depths, to pry into the secrets of its creatures, and to harness its mighty resources will come new problems which, all too frequently, are accompanied by pain and death. One area of activity which has brought man into closer contact with marine organisms in their natural environment than probably any other is that of skin diving-be it professional, or merely for pleasure. Skin diving has become one of the world's fastest growing sports. It is estimated that there are more than one million skin divers in the United States alone, and still the field continues to grow. Numerous deaths have resulted from diving-many of which might have been prevented by adequate technical training. Although skin diving can be considered as a sport, like flying, it requires education, skill, and experience. Stories concerning dangerous marine organisms are legion. While these hair-raising tales may be useful in holding an audience spell-PREFACE bound, a diver at a depth of 100 feet, who suddenly finds himself surrounded by a hungry-looking school of sharks, soon becomes more interested in facts than in fantasy. The bluff of being big and tough wears mighty thin when you mistakenly place your hand into the gaping mouth of a toothy moray eel. Human death-times for even some of the "toughies" reads three to eight minutes, when stung by the deadly sea wasp ! However, it is not the purpose of this manual to throw needless scares into the ...