fresh/salt water weighting....

[Alun]

i've only ever really dived in fresh water, and i may be going away in a couple of weeks to dive in the sea. but i'm not sure about my weighting....

the water will be around 13-14oC. in that sort of temperature i will probably wear a 5mm top and probably 3mm bottoms (maybe 5mm). wearing that in fresh water i would wear a 0.75kg or 1.0kg neckweight depending on the bottoms. i'm guessing about 1.5kg-2kg?? i'll be taking a single neckweight with me, so i want to make sure i take the right amount of weight.

how much should i wear to achieve the same sort of buoyancy in salt water? do you add the same amount of weight regardless of your suit thickness?

alun

 

[alastair]

I think you're going to need alot more in the sea than in a lake.

The rule of thumb they use here is 1kg per mm of suit thickness, but I think it depends on the individual's body.

Without a suit or weights I basically sink, so 5kg is too much. I found 4 to be just right.

Take a kilo too much and ditch it once you get there. It's no fun being too boyant.

Al

 

[Shadowkiller]

Saltwater has about 10-15% more boyancy than freshwater (dead sea not included) but the amount of salt (and therefore water density) varies with the seasons and from place to place.

I have a 5mm lined suit and I dive with 8-9kg of lead around my waist. That gets me neutral at 5-6m.

 

[Bill]

ballast

I've been working on this for a long time. It gets complicated. If you go from 15C distilled water to 15C average salt water, you need to add 4% of your total weight. If I go from the pool to the ocean, 1% is closer. Salt water density in Hawaii changes with run off and some places (the Med?) are saltier. There are no lakes around here to check but temperature is a big factor. Density changes about 1%/3C.
I like Al's idea about the extra kilo. Too many variables. Will you do the same kind of diving?
Aloha
Bill