Here's an interesting trivia quiz I found.  Check your answers at the bottom.

1. Why are J-valves and K-valves so called?

A. They are catalog product codes.

B. The letters refer to the shape of the valve.

C. They are the surname initials of there inventors.

D. They refer to their order of development.

2. Air in a scuba tank can be contaminated with gases like carbon monoxide.

    Can it also contain pollen?

A. Yes.

B.  No.

3. How high above sea level does the atmospheric pressure drop to

    half an atmosphere?

A. 5500 metres

B. 3000 metres

C. 1500 metres

D. 2000 metres

4. Are the majority of fish warm-blooded or cold-blooded?

A. Warm-blooded

B. Cold-blooded

5. Can fish drown?

A. Yes.

B.  No

6. How many hearts does an octopus have?

A. 1.

B. 2.

C. 3.

D.  None.  An octupus is a mollusk and has no heart.

7. In what war did the first attack by a submarine take place?

A. The American War of Independence.

B.  The First World War.

C. The War of The Roses.

D.  The Second World War.

8. Air is 21% oxygen, 78% nitrogen and 1% other gases. What other gases?

A. Mostly Carbon Dioxide.

B. Mostly Argon.

C. Mostly Helium.

D. A Mixture of  Hydrogen and Carbon Dioxide.

9. Nitrogen dissolves into the body's tissues at a rate proportional to the difference

in partial pressures (Henry's Law). Is this also true for oxygen?
A. Yes.

B. No.

10.  What's the best scuba diving Blog you've ever read?

A. H2Andy's

B. H2Andy's

jacknife fish off Jacksonville, Florida

Answers:

1.  Why are J-valves and K-valves so called? 

A. They are catalog product codes. 

In the first US Divers mail order catalogue, each product was given a

letter code. The valves were codes J and K.

2. Air in a scuba tank can be contaminated with gases like carbon monoxide.

Can it also contain pollen?
B.  No.  

Biological material is completely incinerated because of the enormous partial

pressure of oxygen.

3. How high above sea level does the atmospheric pressure drop to half an atmosphere? 

A.  5500 metres  (18,000 feet)

4. Are the majority of fish warm-blooded or cold-blooded? 

B. Cold-blooded.

Most fish do not produce their own body heat. There are, however,  some that are warm blooded.

Most notable among these is the great white shark. Other sharks in the same family are also warm blooded.

5. Can fish drown?
B. No

Fish suffer asphyxiation if the oxygen content of the water falls too far. Also, some sharks have

to keep swimming in order to circulate water over their gills; if they become entangled they can

asphyxiate. Most fish cannot drown (there are a few oddities with lungs that can drown, if you can

name one you are forgiven). What you refer to is not drowning but asphyxiation. Granted many people

use drowning and asphyxia interchangeably, but a quiz can be educational and I feel should not perpetuate

misuse of terms. Drowning refers to beings who do not aspirate in water being suffocated by it. asphyxia -

A condition in which an extreme decrease in the concentration of oxygen in the body accompanied by

an increase in the concentration of carbon dioxide leads to loss of consciousness or death.

6. How many hearts does an octopus have?

C. 3.

7. In what war did the first attack by a submarine take place?

A. The American War of Independence.

The American submarine Turtle attacked HMS Eagle in New York harbour in 1776.

(This is the first authenticated attack by a submarine.)

8. Air is 21% oxygen, 78% nitrogen and 1% other gases. What other gases? 
B.  Mostly Argon. 

Unpolluted dry air at sea level is 78.08% Nitrogen, 20.95% Oxygen, 0.93% Argon,

0.03% Carbon Dioxide, and traces of Ozone and inert gases. Moist air contains 0-4%

water vapour, and polluted air contains fractions of a percent of sulphur gases.

9.  Nitrogen dissolves into the body's tissues at a rate proportional to the difference

in partial pressures (Henry's Law). Is this also true for oxygen?

B. No. 

The oxygen content of body tissues is regulated by the haemoglobin buffer and does not

conform to Henry's Law. [Oxygen toxicity occurs when this system is overwhelmed.]

10.  AS IF...

     recently, i was wondering who came up with the idea of

the neoprene wetsuit? some believe that it was Jacques Cousteau,

but that is not the case (he worked with a somewhat similar material

that never did catch on, while neoprene went on to become the

industry standard).

early design of Bradner suit, 1953

     the inventor of the neoprene wetsuit was Hugh Bradner, working

out of UC Berkely.  Basically, he was the first person to use neoprene

for a protection suit, sometime around 1952. 

dr hugh bradner in los alamos (1943-1946)

     Bradner is an interesting guy... he actually worked on the Manhattan

Project, and helped plan the new laboratory at Los Alamos early on

(see a brief bio). he's been married 61 years; he met his wife

while working at Los Alamos. as far as i can tell, he is still alive.

     neoprene itself was invented by Wallace H. Carothers in 1931. he

worked for the DuPont chemical company, which put the invention into production.

      i've been reading Bill Bryson's A Short History of  Nearly Everything

(great book, i highly recommend it), and he discusses the creation of

the first diving helmet, back in 1823.

     the designer was an englishman, Charles Deane, but the helmet

actually was not intended for diving.  it was intended as a helmet for firefighters.

    here's what Bryson has to say:

     [Deane's helmet] was intended not for diving but

     for firefighting.  It was called a "smoke helmet,"

     but being made of metal it was hot and cumber-

     some and, as Deane soon discovered, firefighters

     had no particular eagerness to enter burning

     structures in any form of attire, but most specially

     not in something that heated up like a kettle and

     made them clumsy into the bargain.  In an attempt

     to save his investment, Deane tried it underwater

     and found it was ideal for salvage work.

 A Brief History of Nearly Everything, p. 241 (2004 ed.)

                 Second-generation dive suit,  as developed by Augustus Siebe

    early on, these suits had a not-insignificant  problem.  That was that

should the air being pumped from the surface stop for some reason

(pump failure being the most common), the pressure differential created

would litterally "suck" the diver into the helmet -- the results were 100% fatal.

    Again, Bryson on the subject:

     Divers sometimes experienced a dreaded

     phenomenom known as "the squeeze."

     This occurred when the surface pumps failed,

     leading to a catastrophic loss of pressure

     in the suit.  The air would leave the suit

     with such violence that the hapless diver

     would, all too literally, be sucked up into

     the helmet and hosepipe.  When hauled

     to the surface, "all that is left in the suit

     are his bones and some rags of flesh,"

     the biologist J.B.S. Haldane wrote in 1947,

     adding, for the benefit of doubters,

     "This has happened."

A Brief History of Nearly Everything, p. 241 (2004 ed.)

    at some point, a reverse valve was invented that would shut off if the

pump at the surface failed.  That way, the air in the suit would not be

able to rush to the surface, taking the flesh of the diver with it.  The

reverse valve didn't solve everything, though... the diver was still

at depth with a very limited supply of air (whatever was in the suit

before the pump failed).

  those guys sure earned their pay, in my book.