Water as weight rather than lead?

[Big Toes]

um sorry i just looked at what i wrote and want to correct a couple of things: if you normally dive salt and want to dive fresh, might want to take off a few pounds. if you normally dive fresh (quarries) then you might want to add a couple of pounds when you get out in the ocean. sorry for the confusion.

erik

 

[viceroy]

It's a pity Mercury is so toxic...it would be wonderful as ballast for scuba.

With a Specific gravity of over 13, it's more dense than lead, and being liquid at room temp would make it so my more comfortable to wear that lead as it would conform to your body's shape

 

[seaducer]

LOL - last year I met a guy on a charter who tried explaining to me why shell drysuits were inherently dangerous because if you flooded one "you'd sink like a rock".

He was an instructor ... :11:

... Bob (Grateful Diver)

That is a real popular thought here with chest waders among surf fishermen. And if you try to tell them otherwise they will assualt you! I volunteered to demonstrate it once for a couple of 20$ bills but no one took me up on it

 

[perdidochas]

no completely the opposite assuming all other things being equal. fresh water will sink below the level of salter water; a good example is the cenotes in mexico. salt water has a higher density due to the salinity level thus the propensity to make people buoyant (so if you normally dive in the ocean, you might want to consider adding some weight if you're diving fresh). but i'm out of this discussion; i originally posted mostly as a joke! (bottom line, if you're seriously looking into using water as a weight you're tool material and should revisit physics 101!)

erik

In the cenotes, the freshwater is on the surface.

Karstgeology: Cenote

Freshwater floats on salt water, as the salt water is more dense.

If you normally dive in the ocean, you want to take off a couple of pounds in freshwater, as you don't float as well in fresh (less buoyancy) as in salt. You've got things very confused.

 

[Soggy]

no completely the opposite assuming all other things being equal. fresh water will sink below the level of salter water; a good example is the cenotes in mexico. salt water has a higher density due to the salinity level thus the propensity to make people buoyant (so if you normally dive in the ocean, you might want to consider adding some weight if you're diving fresh). but i'm out of this discussion; i originally posted mostly as a joke! (bottom line, if you're seriously looking into using water as a weight you're tool material and should revisit physics 101!)

erik

You've got that backwards. In the cenotes, the fresh water is on top. You then go through a halocline into the salt water.

 

[Big Toes]

ok so i'm apparently a tool and got this all wrong; sorry for the confusion! was just trying to convey the differences between diving salt/fresh and weighting requirements.

erik

 

[seibert.kyle]

The reason we use lead is because it is very dense. For something to sink, it must be denser than the liquid. If divers used pumice (has a very low density) they would float, as pumice floats in water. Since we use lead(more dense than water) it helps us sink. If we used water, it would essentially neither float or sink, since it is the same density as the water around it. Contrary to what many of you have said, it is not weight that makes a difference. I would tie 5 tons of pumice to me but it would only make me float more, as it is less dense than water. So if I wanted to sink, I would be better off with 5 lbs of lead.

So thats my science lesson for the day. Hope you enjoyed it and learned a little.

 

[TASims]

I was tempted to read through all 207 posts. but i have to agree with Archimedes on this one, that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid.

 

[H2Andy]

ok, so how about the nautilus?

doesn't it use water as ballast/bouyancy control?

ah, ok, no ... there's gas involved:

In order to swim, the nautilus draws water into and out of the living chamber with the hyponome, which makes use of jet propulsion. When water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood. When water is pumped out, the animal adjusts its buoyancy with the gas contained in the chamber. Buoyancy can be controlled by the osmotical pumping of gas and fluid into or from the camerae along the siphuncles. The control of buoyancy in this manner limits the nautilus; they cannot operate under extreme hydrostatic pressures.

Nautilus - Wikipedia, the free encyclopedia

 

[spectrum]

It makes me want to run down to Home Depot, stock up on PVC pipe and build me one of them!

ok, so how about the nautilus?

doesn't it use water as ballast/bouyancy control?

ah, ok, no ... there's gas involved:

In order to swim, the nautilus draws water into and out of the living chamber with the hyponome, which makes use of jet propulsion. When water is inside the chamber, the siphuncle extracts salt from it and diffuses it into the blood. When water is pumped out, the animal adjusts its buoyancy with the gas contained in the chamber. Buoyancy can be controlled by the osmotical pumping of gas and fluid into or from the camerae along the siphuncles. The control of buoyancy in this manner limits the nautilus; they cannot operate under extreme hydrostatic pressures.

Nautilus - Wikipedia, the free encyclopedia