First, the good news: Lakes and oceans rarely have membership fees. But while you'll avoid the cramped parking lots and smelly changing rooms of a public pool, you'll soon find that to swim in open water is to put yourself at the mercy of the elements.
If you're planning to swim in the ocean, you're probably going to be in for some colder water. In most indoor pools, water is heated to roughly 78 degrees Fahrenheit (25 degrees Celsius). That's a degree of comfort that you won't even find in the tropical waters of Australia, where water temperatures typically hover around 70 degrees Fahrenheit (20 degrees Celsius).
Donning a wet suit is an obvious remedy to colder water, and it can even improve your swim time by up to 20 percent [source: Bernard]. But with wet suits banned at many open water races, it's a good idea to get yourself acclimated to icier waters. Start by taking a bath in cold water. The water will only be slightly chilled at first, but make it gradually colder by adding ice [source: Bernhardt]. The cold tolerance you develop won't merely be psychological: If you spend enough time in chilly water, you'll find your body adapting, too. Just be sure not to get overzealous. If your skin starts to turn blue or white, it's probably time to get out of the tub.
You'll also want to get used to swimming in crowds. Pool races are tidy affairs with swimmers safely isolated to individual lanes. An open water race, on the other hand, is a chaotic mess of scores of swimmers all splashing into the water at the same time.
If you're a beginner, it's best to avoid starting a race in the middle of the pack. For your first race, hang back for a few seconds to let the competitive swimmers pass, and then choose a swimming route slightly outside of the main pack. Keeping to the outside may add a bit of extra distance to your swim, but with all the energy you saved from avoiding the opening struggle, your overall performance will likely improve [source: Bernard].
In the ocean, you'll likely find yourself struggling against hidden currents. One of them, known as a riptide, is a channel of fast-moving water that goes from the beach to the open ocean. If you get yourself caught in one of these you could find yourself out to sea within minutes. Before that happens, simply swim parallel to the shore until you feel the force of the riptide subsiding [source: iSport]. Currents are also one of the main reasons why you shouldn't go swimming in open water without bringing a friend along. Even if your friend doesn't swim, he or she can keep an eye on you from the shore. That way, if you ever find yourself getting dragged into international waters, you at least know you have a buddy who can phone in a rescue helicopter.
Keep reading to find out how to battle waves and swim like a dolphin.