Swimming pool exercises are a great way to lose weight, build muscle, and get in shape. They are low impact, and don't require any extra equipment other than a swimming pool. In fact, the pool does not even need to be large enough to swim laps in. Obviously, one of the easiest ways to get in shape in a pool is to swim, but if you don't wish to swim, or don't have enough room, there are more specialized exercises that target specific areas of the body.
It is beneficial to the body to perform pool exercises, because the water offers a natural resistance in every single workout. This is difficult, if not impossible, to achieve when weightlifting or doing aerobics. Muscles can still become adapted to a static workout, though, so be sure to vary your exercises frequently and to increase the difficulty as things become easier. Pool exercises offer the benefit of fairly quick results. Remember, even though you may not feel sweaty, you still need to stay hydrated when exercising in the water.
If you are in a pool where you can swim, varying the way you swim is a good way to begin. Practice learning different strokes, swimming on your back, or swimming completely underwater. Increasing the speed at which you swim, or the distance you swim before you need to rest, are good indicators of your level of physical fitness.
For other effective pool exercises, begin performing aerobics in the water. You might practice pull-ups on the side of the pool. Begin by using both arms and making small, realistic movements; i.e. do not pull yourself completely out of the pool, and then over-extend your arms when dipping back in. This can injure the upper arms and shoulders. Once you get stronger, you can try to lift yourself with one arm.
If you are proficient at floating on your back, doing crunches in the water while resting your feet on the side of the pool is a great way to exercise. Again, do not splash heavily back into the water. The better you can control your movements, the better your workout will be. Weight lifting in the water is also effective; fitness stores sell weights that are specially designed for use in the pool.
Other simple pool exercises include walking briskly or jogging in the pool. This offers many of the benefits of swimming at an easier level that still provides an aerobic workout with resistance. Taking a class at a local gym can also be beneficial - many gyms offer classes in aqua aerobics, aqua strength training, aqua games, or even aqua kick-boxing.