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Currents can be separated into three categories: • Standing • Tidal • Transitory Standing currents are regular, steady currents that do not change very much, if at all. In many parts of the world, longshore currents normally flow in one direction along the coast. This is a good example of a standing current. The Gulf Stream in the Atlantic Ocean flows from the Caribbean north toward Nova Scotia and then around to Europe. This is an open-ocean standing current. Rivers and streams are also examples of standing currents. You must be aware of the speed and direction of any standing current present where you plan to dive and account for it in your dive plan. Tidal currents are caused by tides. When these currents pass through restricted areas, they can be quite strong, even strong enough to sweep you away no matter how hard you swim. Most divers cannot swim any faster than 1.8 kilometers per hour (1 knot) for longer than a few minutes. Many tidal currents are 3.7 kilometers per hour (2 knots) to 9 kilometers per hour (5 knots) or faster. In areas with strong tidal currents, you must consult tide and current tables, which are readily available, to help plan your dives for slack-water periods only (a time when there is no tidal current). Transitory currents are currents that suddenly appear and disappear. A good example of a transitory current is a rip current caused by surf (figure 8-15). Rip currents occur near the shore and form when wave or wind action pushes water up onto the shore and the water then funnels back out to sea through a narrow passage. This passage or restriction can be a narrow opening in a reef, sandbar, or other large formation otherwise channeling the return of water to the ocean. The offshore flow of a rip current is narrow and can be quite strong. If you find yourself being carried away from shore or you are unable to make progress when trying to return to the beach, you might be in a rip current. You can escape these currents by swimming across the rip current, usually parallel to the shore. Once you are out of the current, you can then turn towards shore and swim in. The rip current might empty into a longshore current. If you try to swim out of the rip current and into the longshore current, the longshore current will push you back into the rip current. If this happens, swim out of the rip current in the other direction. With experience, you will be able to easily identify rip currents. If they occur in your area, your instructor will familiarize you with them and the areas in which they appear. You can also use currents to carry you to your planned exit point, which adds to the ease and enjoyment of your dive. When you take the NAUI Advanced Scuba Diver course, you will learn how to use currents to make ocean diving easier and more exciting. As a new diver, you must learn more about local currents and how to recognize them before you attempt to make unsupervised dives. The best way to accomplish this is by training with a NAUI instructor who has experience in your local area. Even with experience, advanced divers should ask local divers about local current and diving conditions when they plan on diving at a new site. If you travel to a new area where conditions differ from those where you trained, get a local orientation. For example, if all of your diving has been in freshwater lakes, you will need an orientation to dive in the ocean, and vice versa. Or, if you learned in Florida but want to dive in the kelp forests of California, you also need an orientation. NAUI Scuba Diver 184 Diving Environment FIGURE 8-15. YOU CAN EASILY IDENTIFY RIP CURRENTS ONCE YOU KNOW WHAT THEY LOOK LIKE.


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