PADI OPEN WATER EXAM STUDY GUIDE QUESTIONS WITH CORRECT ANSWERS GRADED TO PASS

When is an object positively buoyant? - When it displaces a volume of water weighing more than its own weight. When is an object negatively buoyant? - When it displaces a volume of water weighing less than its own weight. When is an object neutrally buoyant? - When it displaces a volume of water weighing the same as its own weight. Why two pieces of equipment do you use to control your buoyancy? - BCD, Lead weight What does buoyancy help with when you are underwater? - Controlling where you are What does buoyancy help with when you are at the surface? - Floatation, conserving energy How does the buoyancy of an object differ in fresh/salt water? - More buoyant in salt than fresh When you exhale what happens? - Lung volume decreases so you have less buoyancy. When you inhale what happens? - Lung volume increases so you have more buoyancy. Why don't you feel air pressure? - Your body is primarily liquid, which is incompressible and distribute pressure equally throughout your whole body. Where are some air spaces located in the body? - Ears, sinuses, lungs Do you always feel the pressure in body air spaces? - Only if the pressure is different inside and outside the air spaces. 1 bar is what depth? - 0m/0ft 2 bar is what depth? - 33ft/10m 3 bar is what depth? - 66ft/20m 4 bar is what depth? - 99ft/30m How is air volume affected when depth is increased? - It decreases How is air density affected when depth is increased? - It increases What happens if you take an air volume underwater with you in a flexible container or inverted jar? - As pressure increases the volume decreases, same air but smaller space. How do you maintain air volume as you descend? - Equalize What is a "squeeze"? - As volume decreases, pressure pushes body tissues inwards toward air space, causing discomfort. Pressure outside air space is more than pressure inside air space. Where can you get a squeeze? - Ears, sinuses, mask, lungs, teeth How do you equalise air spaces in ears? - Blow and squeeze nose, wiggle jaw, swallowing How often should you equalise? - Every metre before discomfort What do you do if you feel discomfort? - Ascend until discomfort eases, equalise, continue descent slowly Why can't you scuba while sick? - Congestion can plug air passages so you can't equalize What is mask equalisation? - exhale into mask by nose What does your nose need to be in the mask? - To equalize First rule of diving - Always breathe continuously What happens if you hold your breath during ascent? - Lung over expansion, forces air into bloodstream and chest cavity, leading to paralysis or death. What is a reverse block? - When air cannot escape from a air space during ascent How do you react to reverse block? - Slow/stop ascent and give air time to work its way out As you go deeper you use your air ___? - faster Why do you wear a mask underwater? - Light behaves differently in water than in air, which affects how your eyes focus. Mask creates air space so your eyes can focus. How do you know a mask fits? - "Sniff" test Two most important selection factors when buying scuba equipment is? - fit and comfort Features you look for in a mask - low profile nose or finger pockets wide vision field adjustable strap comfortable skirt tempered-glass lens plate Why use snorkels? - Rest or swim with face in water, not wasting cylinder air Features of snorkel - large bore not too long smooth round bends Types of BCDs - front mount, back mount, jacket style What BCD is most commonly used? - jacket style Why do divers need a BCD? - To regulate buoyancy How do you prevent water from entering your scuba tank? - Never completely drain it of air pressure Features of BCD - Hold enough air large deflation hose low pressure inflation system relief valve comfortable fit What are the most common sizes of cylinder capacity - 8,10,12,15 litres 3 types of valves - K, J, DIN What is the J valve - has built in mechanism that signals when you are low on air What is K valve - simple on/off valve What is DIN valve - Screw regulator into valve What is the O-ring - Located in valve, when cylinder and regulator connect forms air tight seal (O-ring)