1. WATER PRESSURE

2. http://www.youtube.com/watch?v=dL08xX4lBQg &feature=grec_index

3. Even though we do not feel it, 14
Even though we do not feel it, 14.7 pounds per square inch (psi) of pressure are pushing down on our bodies as we rest at sea level. Our body compensates for this weight by pushing out with the same force.

4. The pressure exerted by water is called hydrostatic pressure.
Since water is much heavier than air, this pressure increases as we venture into the water.
The pressure exerted by water is called hydrostatic pressure.
For every 33 feet down we travel, one more atmosphere (14.7 psi) pushes down on us. For example, at 66 feet, the pressure equals 44.1 psi, and at 99 feet, the pressure equals 58.8 psi.
To travel into this high-pressure environment we have to make some adjustments. Humans can travel three or four atmospheres and be OK. To go farther, submarines are needed.

5. An amount of air at higher altitudes is less compressed and therefore takes up more volume than air at sea level. A balloon inflated and tied off at sea level will expand as it rises in the atmosphere.

6. Because pressure increases with ocean depth, air is compressed and takes up less volume than at sea level.
A balloon inflated and tired off at sea level will compress as it descends in the ocean.

7. Animals that live in this watery environment undergo large pressure changes in short amounts of time.
Sperm whales make hour-long dives 7,380 feet (2,250 meters) down. This is a pressure change of more than 223 atmospheres!
By studying and understanding how these animals are able to withstand great pressure changes, scientists will be able to build better tools for humans to make such journeys.

8. SO HOW CAN THEY DO THIS?
The ribcage is flexible to allow lung collapse, and the heart rate can decrease to preserve oxygen supplies. Blood can be directed towards the brain and other essential organs only when oxygen levels deplete.
The huge heads of sperm whales contain a large cavity, the spermaceti organ, filled with a waxy liquid called spermaceti oil. This wax can be cooled or heated, possibly by water sucked in through the blowhole, and thus shrinks and increases in density (helping the whale sink), or expands and decreases in density (helping the whale rise to the surface.

9. BOYLES LAW
Under constant temperature, gas will compress as pressure is applied. The volume of a fixed amount of gas is inversely proportional to the total amount of pressure applied. If the pressure doubles the volume shrinks to half.

10. LET’S DIVE!
Cartesian Diver Lab

11. THE DIVER YOU MADE
When the pressure was increased by squeezing the container, the pressure on the water increases the pressure on the air bubble in the diver. Squeezing bottle pushes water into the diver replacing the air bubble with water.
The air compresses and reduces in volume, allowing more water to enter the dive. (increase in pressure decrease in volume)

12. HUMAN DIVING http://www.youtube.com/watch?v=0B0EhuxJsts
Any injury related to pressure is called barotrauma.
There are three kinds of barotrauma: injuries occurring on descent, injuries occurring on ascent and nitrogen narcosis

13. YOU ASKED
Q: What happens to a balloon when it is released into the air?
A: Pressure is decreasing so the volume of the air in the balloon is increasing. So eventually yes the balloon will pop. Although sometimes, the expansion increases the microscopic holes that the helium is already leaking out of, and it leaks faster until the balloon sinks back to Earth.

14. EFFECTS OF PRESSURE ON THE BODY
 If a human spends much time diving at high pressure the tissues in his body become saturated with gas kept compressed and dense by the high pressure.
If the diver comes to the surface too fast, the gas forms bubbles in the body which can cause serious harm and even death. This unpleasant condition is known as "the bends".  
To prevent this, human divers have to decompress very slowly after a deep dive. The decompression process after a deep dive can take days.

15. Injuries on Descent: the pressure of descent presses on the divers membranes of the eyes and ears and can crush bones if deep enough.
Injuries on Ascent: A sudden decrease in pressure from rising out of the water can cause gas to come out of liquids.
Air can come out of the divers blood and travel through the bloodstream, lodging in the brain, heart or lungs- this is called an air embolism and can result in a stroke, heart attack and even death.
Nitrogen narcosis results from breathing in nitrogen gas under pressure. (the high concentration of nitrogen is seawater)
This causes behavior similar to that of alcohol intoxication and can pose problems for the divers safety.

16. VIDEO
Scuba diving dangers

17. Self Contained Underwater Breathing Apparatus. SCUBA
SCUBA DIVING
Self Contained Underwater Breathing Apparatus. SCUBA

18. HISTORY
Ancient swimmers used cut hollow reeds to breathe air, the first basic snorkel used to enhance our abilities underwater. Around 1300, Persian divers were making basic eye goggles from the thinly sliced and polished shells of tortoises. By the 16th century, wooden barrels were used as primitive diving bells, and for the first time divers could travel underwater with more than one breath of air, but not much more than one.

19. HISTORY
In 1771, British engineer, John Smeaton invented the air pump. A hose was connected between the air pump and the diving barrel, allowing air to be pumped to the diver.
In 1772, Frenchmen, Sieur Freminet invented a rebreathing (closed circuit) device that recycled the exhaled air from inside of the barrel, this was the first self-contained air device. Freminet's invention was a poor one, the inventor died from lack of oxygen after being in his own device for twenty minutes.

20. In 1876, Englishmen, Henry Fleuss invented a closed circuit (no air leaves), oxygen rebreather. His invention was originally intended to be used in the repair of an iron door of a flooded ship's chamber. Fleuss then decided to use his invention for a thirty-foot deep dive underwater. He died from the pure oxygen; oxygen is toxic to humans under pressure.
The first commercially successful scuba sets were the Aqualung open-circuit units developed by Emile Gagnan and Jacques-Yves Cousteau, in which compressed gas (usually air) is inhaled from a tank and then exhaled into the water adjacent to the tank.

21. Modern scuba diving gear consists of one or more gas tanks strapped to the divers back, connected to an air hose and an invention called the demand regulator. The demand regulator controls the flow of air, so that the air pressure within the diver's lungs equals the pressure of the water.
Rebreather. Closed circuit.
This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open- circuit breathing set. In the armed forced it sometimes is called CCUBA ( Closed Circuit Underwater Breathing Apparatus.

22. VIDEO
45-how-scuba-works-video.htm

23. DIVING SUIT
The earliest recorded attempt at protecting a diver in rigid armor in The oak suit had a viewing port and holes for the diver’s arms to protrude. Water was kept out of the suit by means of greased leather cuffs, which sealed around the operator’s arms.

24. Rubber diving suits were first used in WWII.
The first atmospheric diving suit was designed in the first to incorporate ball and socket type joints.
An atmospheric diving suit was designed in 1882 by the Carmagnolle brothers. Weighed 837 pounds.
Rubber diving suits were first used in WWII.
Today there are dive 5 main types of pressure diving suits
Dive skins
Wetsuits
Semi-dry suits
Dry suits
Hot water suits.

25. DIVING SUIT
Famous magician and escape artist, Harry Houdini (born in 1874) was also an inventor. Harry Houdini astonished audiences by escaping from handcuffs, straitjackets, and locked boxes, often doing so underwater. Houdini's invention for a diver's suit permitted divers, in case of danger, to quickly divest themselves of the suit while submerged and to safely escape and reach the surface of the water.

27.
sharks

28. SUBMERSIBLES
Submersible is a commercial or non-military midget submarine.
Typically transported to the area of operation by a surface vessel or large submarine.
Other than the size the big difference between a submersible and a submarine is that it may rely on a support facility or vessel for replenishment of power and breathing gases.
Submersibles typically have shorter range, and operate underwater almost exclusively, having little function at the surface

29. SUBMERSIBLES
Small unmanned submersibles called "marine remotely operated vehicles" or MROV’s are widely used today to work in water too deep or too dangerous for divers. (Titanic)

30. Manned Submersibles
These submersibles like ALVIN carry people who make direct observations of the deep seas. People can react to surprising and new situations; they can change experiments and devise new ones on the fly. Manned submersibles cannot stay underwater long, however, and crew safety is always an important consideration.

31. Automated Underwater Vehicles
AUVs combine robotics, thrusters, sonar, and sensors with artificial intelligence. They operate without continuous control from people. While most are still experimental, they hold great promise for deep sea exploration because they can perform routine tasks under water for months at a time.

32. Remotely-Operated Vehicles
ROVs like JASON are controlled by people exploring the deep from a safe distance, usually a mother ship on the surface. ROVs often bristle with manipulator arms, cameras, lights and sensors to "see" and "feel" for their operators. ROVs can stay down longer than vehicles carrying people and transmit data constantly.

33. SOUND AT SEA
Sound is a form of energy transmitted by rapid pressure changes in an elastic medium. (A rapid vibration causes molecules in contact to squeeze closer and then move apart.)
The speed of sound is almost 5 times as fast in water as in air.

34. Sound velocity (m/sec)
1,475
1,500
High sound velocity
2,000
Minimum sound velocity
1,000
4,000
6,000
Depth (m)
2,000
Depth (ft)
8,000
Figure 6.23: The relationship between water depth and the speed of sound.
3,000
10,000
High sound velocity
12,000
Fig. 6-23, p. 174

35. The speed of sound in seawater increases as pressure and temperature increase. (Sound travels faster at the warm ocean surface than in deeper colder water. However in very deep waters, the pressure is so great that the that it offsets the temperature and the speed of sound again increases.
Active sonar, the projection and return through the water of short pulses of high frequency sound to search for objects in the ocean, is used to search for objects or ocean conditions of interest to researchers.

36. Figure 6. 26: The principle of active sonar
Figure 6.26: The principle of active sonar. Pulses of high-frequency sound are radiated from the sonar array of the sending vessel. Some of the energy of this ping reflects from the submerged submarine and returns to the sending vessel. The echo is analyzed to plot the position of the submarine.
The principle of active sonar. Pulses of high-frequency sound are radiated from the sonar array of the sending vessel. Some of the energy of this ping reflects from the submerged submarine and returns to the sending vessel. The echo is analyzed to plot the position of the submarine.
Fig. 6-26, p. 178

37. LIGHT DOES NOT TRAVEL FAR THROUGH THE OCEAN
Light is a form of radiant energy that travels as waves through space, air and water.
The wavelength of light determines its color. Shorter wavelengths are bluer and longer wavelengths are redder.

38. Figure 6. 22: Only a thin film of seawater is illuminated by the sun
Figure 6.22: Only a thin film of seawater is illuminated by the sun. Except for light generated by living organisms, most of the ocean lies in complete blackness.
(a) The table shows the percentage of light absorbed in the uppermost meter of the ocean and the depths at which only 1% of the light of each wavelength remains.
Only a thin film of seawater is illuminated by the sun. Except for light generated by living organisms, most of the ocean lies in complete blackness.
(a) The table shows the percentage of light absorbed in the uppermost meter of the ocean and the depths at which only 1% of the light of each wavelength remains
Fig. 6-22a, p. 173

39. Water rapidly absorbs nearly all wavelengths of light.
Only blue and green wavelengths pass through water in any appreciable quantity or for any distance.
Water Transmits Blue Light More Efficiently Than Red

40. White light (all colors) Colors separated for visualization
Wavelength (nm)
300
400
500
600
700
800
Depth (m)
Figure 6.22: Only a thin film of seawater is illuminated by the sun. Except for light generated by living organisms, most of the ocean lies in complete blackness.
(b) The bars show the depths of penetration of 1% of the light of each wavelength (as in the last column of the table).
100
200
Only a thin film of seawater is illuminated by the sun. Except for light generated by living organisms, most of the ocean lies in complete blackness.
(b) The bars show the depths of penetration of 1% of the light of each wavelength (as in the last column of the table).
300
Fig. 6-22b, p. 173