As with any new physical fitness activity, you should start a swimming fitness program slowly and build up gradually. Here are some tips for getting off to a good start from the United States Masters Swimming organization:

• Ease into the routine - during the first week, try swimming for 30 seconds and then resting for 30 seconds. Repeat 10 times.
• Add kicking - do the same as above while kicking, using fins or a kickboard.
• Add variety - vary the length of swimming/kicking time in relation to the resting time. Lengthen the active time to 45 seconds and shorten the resting time to 15 seconds. Make sure your resting time is enough to let you catch your breath.
• Start with two or three days a week, and then add days.
• Don't worry about speed - you can't swim too slowly. Maintain a pace that is comfortable for you.
• Set realistic goals - aim for the attainable, and you won't get discouraged. Goals could include learning to do a particular stroke better or increasing your laps.

Swimming is the most popular fitness activity for all ages. It is exhausting and energizing at the same time, and you can do it for your entire life.

Related information: Lifestyle changes - Exercise | Nutrition channel - Fitness

Source:  US Masters Swimming. Fitness: getting started - starting a swimming routine. March 1, 2002.