You wouldn't be able to swim if you had no buoyancy. You would cut through the water like you do through the air; fall, sink, whatever you want to call it. You only propel through the water with your limbs if your buoyancy is neutral. You float with a life-vest on, you can't dive underwater with a life preserver without a lot of swimming strength (depending on the density and size of the vest). You can't fly through the air because you are more dense than the air. That is how ballast works on a SCUBA diver or submarine, who use weights and compressed air/seawater, respectivelty.

EDIT: I would like to add that a boat floats because of water pressure vs air pressure, not buoyancy.

quote:

Originally posted by psykostx:
You wouldn't be able to swim if you had no buoyancy. You would cut through the water like you do through the air; fall, sink, whatever you want to call it. You only propel through the water with your limbs if your buoyancy is neutral. You float with a life-vest on, you can't dive underwater with a life preserver without a lot of swimming strength (depending on the density and size of the vest). You can't fly through the air because you are more dense than the air. That is how ballast works on a SCUBA diver or submarine, who use weights and compressed air/seawater, respectivelty.

EDIT: I would like to add that a boat floats because of water pressure vs air pressure, not buoyancy.

there is a flaw in your logic. two actually - the boat floats because of displacement. the combination of the boat and the air within the volume it displaces is lighter than water, which is called "bouyancy"

but the other flaw is that heavier-than-water can swim, just like a heavier than air aircraft can fly.

The flaw is in the way you read my logic, not my logic. Displacement is exactly what I described. The water is trying to fill the gap left by the boat, thus, water pressure keeps the boat afloat by pressing on the sides and bottom. It is a similar concept to bouyancy, just a rearrangement of the terms. Buoyancy is from the density point of view, a boats hull uses the pressure of the denser water to push on the hull of the boat. In a sense, the boat is trying to collapse, but because it is rigid, its pushed up instead of crushed. You can only swim without bouyancy if you have super human strength. Just like you could fly if you could flap your arms hard enough to displace enough air downward without displacing the air back upward. So we are both correct, you can use displacement to compensate for lack of bouyancy, which is what a boat does. They are related, and one uses the other, but they are not the same.

EDIT: In the end, buoyancy and displacement are almost the same thing. Bouyancy uses displacement (in a ratio), but displacement does not neccesarily require buoyancy.

So yes, bouyancy uses displacement. A boat just uses different means to achieve displacement. In the end, its all because water is dense and exerts upward pressure dependent on the force of gravity on the water (normal force). In the end both a boat and a swimmer use the normal force of the water as "anti-gravity."

Someone post a formula.

Getting back to the OP, you could swim with armor, if you had enough strength to exert more force on the water than the force of gravity exerts on the water, thus increasing the normal force of the water underneath you to the point where it can support you.

quote:

Originally posted by willcattletown:
There is one "historical" or "mythical" event involving swimming in armour in which there are two versions of the story - in one the swimmer drowns, in the other he lives.

The story of Beowulf tells of the hero engaged in a swimming race, with both participants in full armor.

quote:

Originally posted by psykostx:
Getting back to the OP, you could swim with armor, if you had enough strength to exert more force on the water than the force of gravity exerts on the water, thus increasing the normal force of the water underneath you to the point where it can support you.

so you missed the posts on the first page where I pointed out that it has been done.

and I sincerely doubt, from your incredibly convoluted "explanation" that you have any real understanding of how it actually works - you sound an awful lot like an engineer, to me.