Do any of you know what is the conversion factor to determine the extra amount of weight needed in salt water vs fresh water? Let say you check how much weight you need in a pool (fresh water), how much extra weight do you need to add when you are diving in salt water to achieve neutral buoyancy? Thanks!
Fresh/salt H2o Weight Conversion Table
- Thread starter Zhenqing
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About 4 lbs if you're small 5-6 if large. That's the easy answer... For the longer answer: Salt water weighs 64 pounds per cubic foot, while fresh weighs 62.4 - so add 1.6 lbs for each cubic foot of space you take up...
To determine that - let us suppose you weigh 200 pounds and wear 6 lbs of lead to be neutral in fresh. Take 206 / 62.4 and you take up 3.3 cubic feet of space. Multiple 3.3 x 1.6 and you get 5.28.
Hope that makes sense!
More fun with Scuba Math can be found on our ScubaToys Education Pages
To determine that - let us suppose you weigh 200 pounds and wear 6 lbs of lead to be neutral in fresh. Take 206 / 62.4 and you take up 3.3 cubic feet of space. Multiple 3.3 x 1.6 and you get 5.28.
Hope that makes sense!
More fun with Scuba Math can be found on our ScubaToys Education Pages
the following is not a rule it is for numerical computation only.
Person weighs 120 lbs , convert to Kilograms 120 / 2.2 lbs/kg = 54.54 kg
Persons addt'l lead weight in swimming pool (freshwater) 6 lbs = 2.72 kg
add persons weight and lead weights: 54.54 + 2.72 = 57.26 kg
57.26 kg X 1.034 sg = 59.2 kg
sg : approx. specific gravity(sg) of seawater, depends on your area
59.2 kg - 54.54 kg (persons weight) = 4.66 kg, convert to pounds
4.66 kg = 10 lbs lead weight in seawater.
so if you use 6 lbs in freshwater you will need to add 4 lbs when you get to saltwater depending on the specific gravity of saltwater.
the above computation is for purposes of showing how specific gravity of liquid affects buoyancy. Test what works for you in real life.
Person weighs 120 lbs , convert to Kilograms 120 / 2.2 lbs/kg = 54.54 kg
Persons addt'l lead weight in swimming pool (freshwater) 6 lbs = 2.72 kg
add persons weight and lead weights: 54.54 + 2.72 = 57.26 kg
57.26 kg X 1.034 sg = 59.2 kg
sg : approx. specific gravity(sg) of seawater, depends on your area
59.2 kg - 54.54 kg (persons weight) = 4.66 kg, convert to pounds
4.66 kg = 10 lbs lead weight in seawater.
so if you use 6 lbs in freshwater you will need to add 4 lbs when you get to saltwater depending on the specific gravity of saltwater.
the above computation is for purposes of showing how specific gravity of liquid affects buoyancy. Test what works for you in real life.
Moogyboy
Contributor
For whatever reason, when I went to Florida & Bimini this past May--my first time diving in saltwater--I ended up adding what seemed like a LOT of weight. I usually dive about 9-11 lbs in freshwater with either my 3/2mm shorty or without a wetsuit. In the ocean I had to use about 18 lbs if memory serves. Go figure. I had to abort my first dive because I was so ludicrously underweighted, and got dehydrated and seasick adding weights to my belt on that boat. (This was BEFORE I got on the Blackbeard's boat, btw...no trouble at all later, on the Sea Explorer 
)
cheers
Billy S.
)cheers
Billy S.
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