sandanbob
Contributor
Good morning!
Way back in OW, we were taught that seawater is more dense, hence would require more weight to offset buoyancy. The standard values used are 62.4 lb/cf for freshwater, and 64 lb/cf for seawater (which can actually vary, based on salinity.)
I have been thinking about that, and something that I recently read here made me decide to post. For reference, what I had read was concerning European standards that 'average' the densities, such that a dive computer based on those standards doesn't have separate settings for freshwater vs. seawater. (I am not familiar with those standards, so if I worded it incorrectly, I apologize.)
If you look at those density values and compare them, then you could say that freshwater is 97.5% the density of seawater; or, alternatively, seawater is 102.6% the density of freshwater. So, the difference is about 2.5%. If a diver is wearing 20 pounds (as an example) of weights for seawater, than calculations say you should remove 2.5% (1/2 pound) for moving to freshwater. Or, vice versa, if you are wearing 20 pounds in freshwater, you should be adding 1/2 pound for diving in seawater. If the diver is wearing 40 pounds, then the difference becomes one pound, and so on.
Other threads on SB indicate difficulty in finding 1/2 pound weights. I don't know if that is still the case. It seems that if you were weighted for diving in seawater, you would be fine (assuming the same gear, especially a wet suit,) without being considerably over-weighted in freshwater.
Anyway, just some Sunday morning thoughts.
Be safe!
Bob
Way back in OW, we were taught that seawater is more dense, hence would require more weight to offset buoyancy. The standard values used are 62.4 lb/cf for freshwater, and 64 lb/cf for seawater (which can actually vary, based on salinity.)
I have been thinking about that, and something that I recently read here made me decide to post. For reference, what I had read was concerning European standards that 'average' the densities, such that a dive computer based on those standards doesn't have separate settings for freshwater vs. seawater. (I am not familiar with those standards, so if I worded it incorrectly, I apologize.)
If you look at those density values and compare them, then you could say that freshwater is 97.5% the density of seawater; or, alternatively, seawater is 102.6% the density of freshwater. So, the difference is about 2.5%. If a diver is wearing 20 pounds (as an example) of weights for seawater, than calculations say you should remove 2.5% (1/2 pound) for moving to freshwater. Or, vice versa, if you are wearing 20 pounds in freshwater, you should be adding 1/2 pound for diving in seawater. If the diver is wearing 40 pounds, then the difference becomes one pound, and so on.
Other threads on SB indicate difficulty in finding 1/2 pound weights. I don't know if that is still the case. It seems that if you were weighted for diving in seawater, you would be fine (assuming the same gear, especially a wet suit,) without being considerably over-weighted in freshwater.
Anyway, just some Sunday morning thoughts.
Be safe!
Bob