Misconceptions and Fallacies

[Midnight Star]

...Oh, No! You didn't!...

I just couldn't resist!

-----

Mike.

 

[Pathfinder]

Rock on, rockjock3! Thanks for this one...so will the real truth please stand up?

Isn't it true that human blood in water will attract sharks from miles away????

Potential future bleeders in the water need to know!

Any blood, not just human blood. Sharks detect it at 1 part per million and smell it from a distance of approximately 1/4 mile. Not quite "miles" away.

Dave

 

[CAPT HOOK]

Agree with Walter!!
All these "expert" sources quoting Wikipedia!

 

[matt_unique]

Myth: Back inflate BCs (and BP/Ws) "push your face in the water".

It is possible to end up with your face in the water on the surface, if you have all your weight on a belt on your front and/or you overinflate your BC on the surface and/or you do not simply lean back and relax on the surface.

In any of the possible scenarios above, nothing "pushes your face in the water". The BC bladder floats, and your weight, or the weight of your weights PULL your face in the water by GRAVITY.

There-I never want to hear that myth again

That's a great one I forgot about...and if you're wearing any exposure protection on your legs, it takes a little effort to lean forward wearing a backing inflate rig.

--Matt

 

[miketsp]

Any blood, not just human blood. Sharks detect it at 1 part per million and smell it from a distance of approximately 1/4 mile. Not quite "miles" away.

Dave

Let's not get carried away. 1ppm is actually quite a lot of blood.
Let's take a cylinder of water radius 0.25 miles and say 60ft depth.
Unless my arithmetic is wrong that's 328 million cubic ft.
So to fill that entire cylinder with 1ppm would need 328 cu ft of blood. That's hardly what I'd call a scratch.
Now you may just be unlucky in that the blood drifts down to the shark leaving a fairly concentrated trail...

 

[Temple of Doom]

Agree with Walter!!
All these "expert" sources quoting Wikipedia!

Quoting Wikipedia is perfectly fine if you take it with a grain of salt. Using it as your one and only definiitive source on any topic is suspect. As with anything, you need to use your common sense.

I used Wikipedia to illustrate that surface area was dependant on drag (not to find out that it was), and I backed it up with huge amounts of common sense. I think we can agree that it doesn't take an "expert" to realize that surface area does matter. Again my analogy:

If surface area didn't matter for drag then a mini-cocktail umbrella would be as effective as a parachute when jumping out of a plane.

Being overweighted (needing air in a bc to be neutral) is just a fact of life when diving all but the warmest waters with the smallest tanks.

I suppose, if you're using the definition of being over-weighted as any time you require air in your BC to stay neutral, then I think I've found the reason for the difference of opinion. I think the rest of us were talking about having a bunch more lead on your dive than you needed for propper buoyancy.

Craig

 

[Rick Murchison]

I used Wikipedia to illustrate that surface area was dependant on drag

Huh?
Methinks there's a cart/horse inversion goin' on here...
Rick

 

[Walter]

Quoting Wikipedia is perfectly fine if you take it with a grain of salt.

In that case, what's the point?

 

[Temple of Doom]

Huh?
Methinks there's a cart/horse inversion goin' on here...
Rick

Yerp, it sure is. Drag is dependant on surface area, not the other way around.

Craig

 

[Midnight Star]

myth: You can't measure the seriousness of a sting or contact from a marine animal by how much it initially feels or whether it burns or hurts.

truth: So that was a blue skinned octop ... (falls over).