Exam (elaborations) PADI Open Water

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 7/12/25, 8:37 PM PADI Open Water Diver Certification 2/1 0 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 7/12/25, 8:37 PM PADI Open Water Diver Certification 3/1 0 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