Buoyancy
What is buoyancy?
When
you get into the pool, your body displaces a volume of water (the "hole"
in the water that your body fits into). As long as the water your body displaces
weighs more than you do, you float.
This is basically Archimedes' Law.
You
weigh less than the water you're in, because your lungs are full of air,
like a balloon, and like a balloon, the air in your lungs lifts you to the
surface naturally.
Everyone floats in the water at their own natural level.

Different
factors contribute to how high — or low — in the water you float.
First,
your body type has a lot to do with your buoyancy. Fat floats, as you've probably
heard, while your bones and muscles, denser than fat, are not as willing to
float.
Also, the relative size of your lungs to the rest of your body determines
how high in the water your body will float.
Second, the density of the water is a factor. Saltier water weighs more per unit of volume, so you will float higher in saltier water (the Red Sea, for instance) than you would in fresh water.
Finally,
there is a curious phenomenon of apparently greater buoyancy — for some
people — in deep water.
According to Melon Dash
of the Transpersonal Swimming Institute, “Buoyancy and feeling
buoyancy are two different things.
You can be buoyant but not feel buoyant.
Your buoyancy does not change between the shallow and the deep. Your
feeling of buoyancy may change.
“Feeling buoyancy in water is all about 'presence' in one's body.
Presence — feeling while swimming — is most available when a swimmer
is not distracted by the pool bottom, or anything else.
“The pool bottom is closer in the shallow end and farther away at the
deep end.
Because it's so close in the shallow end and you know you can use it any time,
it may also be a distraction: some of your awareness, that is, some of your
attention or presence is on the bottom.
“When this distraction is not there in the deep end due to the fact that we can't use the bottom there, people often feel more buoyant in the deep: their awareness is all at the surface rather than part of their awareness being at the bottom, as in the shallow.”
A
factor
you CAN control is how relaxed you are. Tense muscles often keep your body
a bit lower in the water, since many people breathe more shallowly and rapidly
when tense (hence less air in the lungs for floating).
Did you ever play the "thinking heavy" game as a kid? You'd be harder
to pick up if you imagined yourself to be as heavy as a piano, easier to pick
up if you pretended to be a balloon.
Again, we each have our natural level of buoyancy. And then, there are those few who don't float at all (far fewer than people realize).
However, no matter how low in the water you float or glide or swim, it has nothing to do with ultimately learning to swim. Period. You'll adjust your stroke, roll your face out a bit more to get your air, and swim.

Test your buoyancy
You'll need a pool, treading water skills for the deep end, a buddy and as always, a lifeguard.Optional: If you chose to, you could let go the ladder and pop up to the surface.
Physics
There
is a lot of material out there dedicated to helping you swim faster, smarter,
better. If you've faced your fear, learned your swim basics and are ready
for high performance, bravo!
You'll be off to other horizons, beyond what Relaxnswim offers.
But
not so fast, my speedy friend! As you've been hearing over and over, your
basics depend on relaxing and not fighting the water. Smart, smart.
Next you'll learn to position your body to reduce the dreaded drag or resistance.
Who's going to work harder than they need to? Not you, smarty.
You'll build upon these facts throughout your swim career, tweaking your style as you better understand how water really works.
Article about swim physics
Total Immersion has a helpful article in their archives:
"Swim
Like a Fish: A Science Report"
http://www.totalimmersion.net/2003%20articles/may/science.html
