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Stuff Every Scuba Diver Should Know

Never hold your breath, equalizing, depth and air, safety stops, gear and hand signals.

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⏱ Timed practice exam

SESK practice exam: 50 questions, 50 minutes, pass with 40 right (80%).

Take it like the real thing: a countdown, no hints until you finish, then your score by topic, every miss explained, and a readiness score from your last 3 exams.

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  1. What is the first rule of scuba diving?
    Show the answer

    Breathe continuously and never hold your breath. Air in your lungs expands as you rise toward the surface. If you hold your breath, that air has nowhere to go and can injure your lungs. Keep breathing slowly and normally the whole dive.

  2. What can happen if a diver holds their breath while ascending?
    Show the answer

    Expanding air can rupture lung tissue. As a diver rises, the air in the lungs expands. Without exhaling, it can tear the lungs (pulmonary barotrauma) and push gas bubbles into the arteries, called an arterial gas embolism.

  3. After breathing from a tank, how shallow can a breath-hold ascent still hurt your lungs?
    Show the answer

    As shallow as 4 feet. Lung injury is about the change in pressure, not total depth. Even in a pool, holding a full breath of tank air on the way up can tear the tiny air sacs in your lungs.

All 63 practice questions

The first 50 are free, with the answer, why it's right and the official sources. The other 13 (🔒) are for SESK members. Or play them as a game and track what you've learned.

Show all 63 questions
  1. What is the first rule of scuba diving?
  2. What can happen if a diver holds their breath while ascending?
  3. After breathing from a tank, how shallow can a breath-hold ascent still hurt your lungs?
  4. Boyle's law says that for a gas at constant temperature, pressure and volume are what?
  5. At 33 feet (10 m) of seawater, what is the total pressure on a diver?
  6. A balloon filled at the surface is carried down to 33 feet. What happens to its size?
  7. Where is the risk of pressure injuries (barotrauma) greatest for divers?
  8. When should divers equalize their ears on the way down?
  9. Without equalizing, about how deep can you go before your ears begin to hurt?
  10. Your ears start to hurt on the way down. What should you do?
  11. Which descent position makes equalizing your ears easier?
  12. Why should scuba divers never wear earplugs or swim goggles?
  13. In the BWRAF pre-dive buddy check, what does the B stand for?
  14. When dive buddies make their plan, whose ability should it be based on?
  15. What ascent rate do the US Navy and NOAA use for divers?
  16. Where and how long is the standard safety stop at the end of a recreational dive?
  17. Why do deeper dives have shorter no-decompression limits?
  18. If you stay within your dive computer's limits, can you still get decompression sickness?
  19. The nickname "the bends" for decompression sickness first appeared among which workers?
  20. What is the most commonly reported first symptom of decompression sickness?
  21. When do signs of decompression sickness usually appear after a dive?
  22. What is the main first aid for a diver with signs of decompression sickness?
  23. What is the definitive treatment for decompression sickness?
  24. In a life-threatening dive emergency, who should you contact first?
  25. Nitrogen narcosis at depth feels most like what?
  26. A diver feels nitrogen narcosis. What usually makes it go away?
  27. After a single no-decompression dive, DAN recommends waiting at least how long before flying?
  28. After several dives a day or several days of diving, DAN recommends waiting how long before flying?
  29. You have possible decompression sickness symptoms before your flight home. What should you do?
  30. A newly certified PADI Open Water Diver is trained to dive to what maximum depth?
  31. What is the maximum depth limit for recreational scuba diving?
  32. You run out of air and your buddy is close by. What is your first move?
  33. Out of air with no buddy near and the surface close, divers learn which emergency skill?
  34. What does the recreational "diver down" flag look like?
  35. What does a scuba BCD help you control?
  36. Which part of a scuba regulator attaches to the tank and reduces high pressure?
  37. When does a scuba regulator second stage deliver air?
  38. What is the spare second stage on your regulator, the alternate air source, for?
  39. Which scuba instrument displays remaining tank pressure?
  40. An aluminum 80 scuba tank filled to 3000 psi holds about how much air?
  41. Doing a weight check with an empty BCD and a normal breath, where should you float?
  42. In cooler water, a thicker wetsuit mainly provides more of what?
  43. How do you clear water from a scuba mask?
  44. What is a standard way to stop a dive mask from fogging?
  45. What is the first fin kick most new scuba divers learn?
  46. Which hand signal means OK to a scuba buddy?
  47. What does a thumb up mean underwater?
  48. What does a thumb down signal mean on a dive?
  49. How does a diver signal out of air?
  50. Which hand signal tells your buddy something is wrong?
  51. How do you signal low on air? 🔒
  52. Using the rule of thirds, when do you turn back toward your exit point? 🔒
  53. What should you do if caught in a strong current during a drift dive? 🔒
  54. Why should divers avoid touching coral? 🔒
  55. What should you do if you see a lionfish on a dive? 🔒
  56. What is the first safety rule for jellyfish on a dive? 🔒
  57. Why do divers do the stingray shuffle on shore entries? 🔒
  58. What is the maximum depth for a PADI Advanced Open Water Diver age 15 or older? 🔒
  59. Before scuba training, what should you do about a heart or lung condition? 🔒
  60. What is one way to reduce seasickness before a dive? 🔒
  61. Small buoyancy adjustments during a dive are often made by using what? 🔒
  62. What is in a standard recreational scuba cylinder? 🔒
  63. Which fin style is designed to be worn with dive boots? 🔒