Most people can float but some who have a higher ratio of muscle to fat may not be able to. Such people also find it harder work to swim, which is why purebred colored people don't often feature in world swimming competitions. But you don't have to be fat to be able to float. In general ladies can float more easily than men.
The popular view of floating is of somebody lying on the back with arms apart stretched above the head. And there's reason in this picture. Lying on the back enables breathing, and the extended arms balance the body, with the centre of flotation being around the lungs.
Most people can draw enough air into the lungs to inflate a moderate sized rubber ring. So from this it follows that fully inflated lungs are a great help in floating. When air is expelled from the lungs however, the lungs cease to provide this help. The answer is to modify the normal breathing cycle. For floating, and in other swimming disciplines air is drawn in to fill the lungs and held there for a few seconds. The air is then expelled rapidly and just as rapidly inhaled again. Thus the lungs remain fully inflated for some 90% of the breathing cycle, greatly assisting in the buoyancy of the body.
Here is an exercise that I do from time to time. Adopt the horizontal floating position with the arms above the head and the legs spread and establish the breathing pattern. Bring the legs together and very slowly bring the arms down to the side. As you do so the change of shape will bring you to a vertical position. Maintaining the breathing pattern you can stay in this vertical position, head tilted back to keep nose and mouth above water.
Reversing the procedure, moving arms and legs slowly, will bring you back to the initial position on your back.
Here are some exercises to practice. They all involve movement and the first two are easier than the exercise described above.
1)The coracle - A coracle is a small round boat that is propelled
by hand or a short paddle and can be spun on its axis. Float face up in
the water with knees apart and ankles crossed and head forward so that
you bend in the middle. Now by paddling with your hands you will be able
to spin around in either direction.
2)Sculling - Float on the back, legs straight together, arms by
the side. Now propel yourself by small rotary motions with the hands.
It's possible to go forward or back with a little practice or even turn
round in the water, keeping the body straight.
3)Torpedo - This is an advanced exercise. Float on the back, legs
straight together and with the arms straight above the head, brushing
the ears. Do the rotary sculling motion with the hands to propel the body
feet first. The hands represent the screw of a torpedo, hence the name.
Do not dismiss the importance of floating in swimming. Being able to float and rest has saved many lives, but it does take practice and confidence to do it for any length of time. Floating is easier in salt water which is good to know if you get into trouble in the sea.
When I was a young man I belonged to a swimming club and played water polo. The ladies in the club became jealous and formed a floating section under a coach and became famous all over London for their displays. It was probably the fore-runner of synchronised swimming, but in my opinion far more entertaining. And without the nose clips.
One set involved the ladies floating side by side, head to feet. On the command each lady grasped the ankles of the ladies on each side. On the next command they commenced to slowly push away so that they opened like a trellis. What was quite amazing that the display expanded such a long way. You may be interested to try this with one or more friends. Of course, the more people that take part, the more difficult it becomes.
Other sets involved the same principle but in closed circular forms which, with the lady's colourful costumes were quite spectacular. Rather like the Hollywood swimming spectaculars.
Floating techniques are an important part of swimming and deserve attention.