The adult population suffers usually and naturally a general decline in physical fitness condition. Swimming is one of the appropriate ways for this population to keep in shape. 

Swimming improves physical fitness and can help quite effectively dealing with muscle and joint pain including back pain and shoulder. 

Being persistent in training and include muscle strengthening exercises, flexibility and coordination, working on properbreathing and strengthening the joints and bones will positively affect your physically and mentally health and keep you in good spirit.

Unlike other aerobic exercise, while swimming it is more difficult to increase heart rate, because the water is carrying the body weight. So if you wish to take care of your heart health, you should dedicate at least three times a week for at least some 45-60 minutes for training.

Front crawl is the most recommended style and is considered as very effective as it causes the least strain on the neck (comparing to breaststroke, for example).

If for any reason you haven't taken any lessons when you were younger, take some lessons now. There's nothing wrong with starting in our advanced age. You will get skilled as much as you practice.

Swimming in the sea is quite different. It needs more skills and practice and sometimes it is even quite challengeable.

Subscribe to the local municipal swimming pool or local country club and make it a regular habit and don't find any excuses to avoid it. Do it on a regular basis and see how enjoyable it is.