SDI SCUBA CERTIFICATION STUDY GUIDE
2026/2027 – REAL EXAM QUESTIONS WITH
100% VERIFIED CORRECT ANSWERS PACK.
◎ Density. ANSWER:- How heavy something is for its size.
◎ Light absorption. ANSWER:- Light gets dimmer the deeper you go.
◎ Refraction. ANSWER:- Water bends light and makes things look closer and bigger.
◎ Color loss. ANSWER:- Colors fade with depth, starting with red and orange.
◎ Sound underwater. ANSWER:- Sound travels faster and is hard to locate.
◎ Heat loss. ANSWER:- Water pulls heat from your body quickly.
◎ Pressure. ANSWER:- Increases as you go deeper underwater.
◎ Barotrauma. ANSWER:- Injury caused by trapped air expanding or shrinking.
◎ Equalization. ANSWER:- Balancing pressure in your ears and mask.
◎ Mask squeeze. ANSWER:- Mask presses on your face if not equalized.
◎ Ear squeeze. ANSWER:- Pain from pressure if ears are not equalized.
◎ Reverse block. ANSWER:- Trapped air expands during ascent and causes pain.
◎ Sinus squeeze. ANSWER:- Pressure pain in your forehead or face when
descending.
◎ Tooth squeeze. ANSWER:- Pain in teeth from trapped air while diving.
◎ Boyle's Law. ANSWER:- As pressure goes up, air volume goes down.
◎ Charles' Law. ANSWER:- Air expands when it gets warmer.
◎ Dalton's Law. ANSWER:- More pressure means more gas goes into your body.
◎ Nitrogen absorption. ANSWER:- Your body takes in more nitrogen at depth.
, ◎ Nitrogen release. ANSWER:- Nitrogen leaves your body when you ascend slowly.
◎ Decompression sickness. ANSWER:- Bubbles form in your body from surfacing too
fast.
◎ Nitrogen narcosis. ANSWER:- Feeling dizzy or silly from too much nitrogen.
◎ Safety stop. ANSWER:- A pause at 15 feet to let nitrogen leave your body.
◎ Ascent rate. ANSWER:- How fast you go up from a dive.
◎ No-decompression limit. ANSWER:- Max time you can stay at a depth without stops.
◎ Dive computer. ANSWER:- Device that tracks depth, time, and nitrogen load.
◎ Dive tables. ANSWER:- Charts that show safe dive times and depths.
◎ Surface interval. ANSWER:- Time spent on the surface between dives.
◎ Overexertion. ANSWER:- Pushing your body too hard while diving.
◎ Hyperventilation. ANSWER:- Breathing too fast which lowers carbon dioxide.
◎ Buoyancy. ANSWER:- The ability to float, sink, or hover.
◎ Positive buoyancy. ANSWER:- When you float on the surface.
◎ Negative buoyancy. ANSWER:- When you sink underwater.
◎ Neutral buoyancy. ANSWER:- When you stay still underwater without moving up or
down.
◎ BCD. ANSWER:- Device that helps you float or sink.
◎ Weight system. ANSWER:- Helps you go underwater safely.
◎ Buoyancy check. ANSWER:- Testing your weight to float at eye level.
◎ Trim. ANSWER:- Your body position while swimming underwater.
◎ Regulator. ANSWER:- Delivers air from your tank to your mouth.
◎ Alternate air source. ANSWER:- A second regulator for emergencies.
2026/2027 – REAL EXAM QUESTIONS WITH
100% VERIFIED CORRECT ANSWERS PACK.
◎ Density. ANSWER:- How heavy something is for its size.
◎ Light absorption. ANSWER:- Light gets dimmer the deeper you go.
◎ Refraction. ANSWER:- Water bends light and makes things look closer and bigger.
◎ Color loss. ANSWER:- Colors fade with depth, starting with red and orange.
◎ Sound underwater. ANSWER:- Sound travels faster and is hard to locate.
◎ Heat loss. ANSWER:- Water pulls heat from your body quickly.
◎ Pressure. ANSWER:- Increases as you go deeper underwater.
◎ Barotrauma. ANSWER:- Injury caused by trapped air expanding or shrinking.
◎ Equalization. ANSWER:- Balancing pressure in your ears and mask.
◎ Mask squeeze. ANSWER:- Mask presses on your face if not equalized.
◎ Ear squeeze. ANSWER:- Pain from pressure if ears are not equalized.
◎ Reverse block. ANSWER:- Trapped air expands during ascent and causes pain.
◎ Sinus squeeze. ANSWER:- Pressure pain in your forehead or face when
descending.
◎ Tooth squeeze. ANSWER:- Pain in teeth from trapped air while diving.
◎ Boyle's Law. ANSWER:- As pressure goes up, air volume goes down.
◎ Charles' Law. ANSWER:- Air expands when it gets warmer.
◎ Dalton's Law. ANSWER:- More pressure means more gas goes into your body.
◎ Nitrogen absorption. ANSWER:- Your body takes in more nitrogen at depth.
, ◎ Nitrogen release. ANSWER:- Nitrogen leaves your body when you ascend slowly.
◎ Decompression sickness. ANSWER:- Bubbles form in your body from surfacing too
fast.
◎ Nitrogen narcosis. ANSWER:- Feeling dizzy or silly from too much nitrogen.
◎ Safety stop. ANSWER:- A pause at 15 feet to let nitrogen leave your body.
◎ Ascent rate. ANSWER:- How fast you go up from a dive.
◎ No-decompression limit. ANSWER:- Max time you can stay at a depth without stops.
◎ Dive computer. ANSWER:- Device that tracks depth, time, and nitrogen load.
◎ Dive tables. ANSWER:- Charts that show safe dive times and depths.
◎ Surface interval. ANSWER:- Time spent on the surface between dives.
◎ Overexertion. ANSWER:- Pushing your body too hard while diving.
◎ Hyperventilation. ANSWER:- Breathing too fast which lowers carbon dioxide.
◎ Buoyancy. ANSWER:- The ability to float, sink, or hover.
◎ Positive buoyancy. ANSWER:- When you float on the surface.
◎ Negative buoyancy. ANSWER:- When you sink underwater.
◎ Neutral buoyancy. ANSWER:- When you stay still underwater without moving up or
down.
◎ BCD. ANSWER:- Device that helps you float or sink.
◎ Weight system. ANSWER:- Helps you go underwater safely.
◎ Buoyancy check. ANSWER:- Testing your weight to float at eye level.
◎ Trim. ANSWER:- Your body position while swimming underwater.
◎ Regulator. ANSWER:- Delivers air from your tank to your mouth.
◎ Alternate air source. ANSWER:- A second regulator for emergencies.
