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Dave, How much does water weigh in water ? How much does a body weigh in water ? How much does a liver weigh inside a body ? . . . in water ? Will Bret's gut hang over his belt in the water ? Yes, gravity and MASS are here to stay but weight is a relative thing . How much would a 5 lb lead weight weigh if it were measured while accelerating towards the earth at 16 ft/sec squared in a falling plane ? The mass you measured would be the same but the weight you measured would change. If the hydrostatic pressure of the water were not transmitted throughout the body then parts of it would collapse. Since it is, then everything immersed in those elements of the body that transmit that pressure (body fluids, blood, lymph, . . ) is as if it were in the surrounding water (as if the body were a bag of water with variably denser pieces of stuff in it). I think what matters is that some of the organs and muscles are able to change shape due to the support of buoyancy and so present a different resistance to the flow of blood through them by virtue of their reduced degree of compression by gravity. The heart, lungs, and kidneys would probably not feel much, if any, difference but the muscles of the legs, the viscera, and anything else that had a tendency to sag in air would be buoyed up in a way that changed the physical tissue tension and perhaps the blood flow through them. (I would think that the firmer you are the less difference this would make in the flow of blood) There can still be pooling of blood in the lungs and chest cavity in general because the shape of the tissue around them is not appreciably altered by buoyancy (except perhaps for the effect of buoyancy on the viscera under the diaphragm). Another thing that effects pooling everywhere is muscle activity and the ability of the chest cavity to return to it's normal relaxed shape and volume. The heart does not force blood back to itself under muscle power but by the elastic nature of the heart muscle returning to it's resting volume and shape (like the bulb of a baster). If the chest cavity is squeezed by a tight wetsuit so that the heart can not return to this shape then blood under pressure of the pumping action will pool or back up into the organs. This can kill you in the short time of a typical recreational dive. Chuck -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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