What's fsw?

[junior]

I've been seeing posts about wrecks and they are using some kind of unit measure (i.e., "...sitting at 225 fsw"). What is this measure?

 

[Tom]

fsw is feet of salt water. As opposed to ffw - feet of fresh water. Actually if you are 100 feet deep in salt water you are the same distance from the surface as if you were 100 feet deep in fresh water. ( I looked it up - yup - 100 feet is 100 feet ).

The difference is salt water is slightly heavier than fresh water. At shallow depths it's no big deal but on deeper dives that extra little per foot starts adding up. A 200 foot dive in salt water will have to be treated differently than fresh water as far as deco time and air consumption and surface interval and things like that.

Tom

 

[Walter]

........if your depth gauge or computer measures in fsw (feet of sea water) and you are in fresh water you can ignore the actual difference in depth with regards to deco status. Assuming you are not at altitude, treat the dive as if you were in the ocean instead. You are actually slightly deeper than your equipment is measuring, but since it is pressure, not depth, that matters you can ignore the difference.

Walter

 

[greg somers]

between us real salt water divers and the unlucky pretenders who dive in fresh water...( we'll see what that stirs up..heheheh :boom: ) It just makes them feel better about themselves.....eace:
The Thunder from Down Under,
The one and only,
The Gasman.

 

[joewr]

Actually a pound of sea water WEIGHS the same as a pound of fresh water--or a pound of feathers! On the other hand a quart of sea water weighs more than a quart of fresh water because it is more DENSE. This is, or course, due to the greater amount of dissolved salts--mainly NaCl.

Good night all!

Joewr

 

[L. Smallman]

Hi Junior,

I'm just curious what agency did you certify with and what level of certification have you achieved. The fsw info. was in the Padi Open Water manual. No offense meant, but this might be the perfect place to remind folks that it's always a good idea to brush up on the old training manual once in a while. Even avid and frequent divers can reap benefits from periodic refreshers.

Laura

 

[junior]

I was certified in PADI open water school in July 2000. I'm sure Dave covered it, but I don't remember details like that. I'm a graduate aerospace engineer from Embry-Riddle University in Daytona Beach. I know about the different denisity values between fresh and salt water. I just didn't catch on to the measure unit.

What I remember from open water dive class is don't hold your breath while diving, equalize early and often, never ascend faster than your bubbles, and stop at 15' for 3 minutes on the way back up.

 

[Walter]

All good information except, "never ascend faster than your bubbles." We used to teach, "never ascend faster than your smallest (foam) bubbles" back when the standard ascent rate was taught as 60 ft per minute. Today, almost everyone agrees 60 ft per minute is too fast. Dan and many agencies recommend an ascent rate of 30 ft per minute. Unfortunately, PADI's GO DIVE manual still uses 60 ft per minute.

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[Swamp Rat]

of sea water weighs more than a quart of fresh water because it is more DENSE.

??? what does the Salt water being stupid have to do with it???

 

[Walter]

........density refers to how much mass is in a given volume. When an object is denser than another it's harder to penetrate with anything including information. Density doesn't make it stupid, merely more difficult to educate. Once you get the info in, it reasons as well as fresh water.

WWW™