| No. | Item | Definition |
|---|---|---|
| 1. | apnea | breath-hold diving |
| 2. | ascent | movement upward to surface |
| 3. | ballast | added weight for buoyancy control |
| 4. | bifins | separate fins for each foot |
| 5. | blackout | loss of consciousness underwater |
| 6. | blade | flat fin section for thrust |
| 7. | bottom time | time spent underwater |
| 8. | breathe-up | pre-dive breathing routine |
| 9. | buddy | diving partner for safety |
| 10. | buoyancy | upward force in water |
| 11. | carbon | light stiff fin material |
| 12. | CO2 | carbon dioxide in the body |
| 13. | constant weight | discipline with same carried weight |
| 14. | contraction | breathing-muscle spasm during apnea |
| 15. | counterweight | line system assisting ascent |
| 16. | current | moving water flow |
| 17. | defog | prevent mask from misting |
| 18. | depth | distance below the surface |
| 19. | descent | movement downward underwater |
| 20. | dive | go underwater intentionally |
| 21. | drag | water resistance against movement |
| 22. | duck dive | surface entry headfirst downward |
| 23. | dynamic | horizontal breath-hold swimming |
| 24. | eardrum | membrane separating outer and middle ear |
| 25. | equalization | pressure balancing technique |
| 26. | equalize | balance pressure in ears and mask |
| 27. | exhale | breathe air out |
| 28. | fiberglass | common fin blade material |
| 29. | fins | footwear for underwater propulsion |
| 30. | float | surface buoy for support |
| 31. | flood | fill with water |
| 32. | foot pocket | part holding the foot |
| 33. | free immersion | line diving using arm pulls |
| 34. | freedive | dive on one breath |
| 35. | freefall | drift downward without kicking |
| 36. | Frenzel | equalization using tongue and throat |
| 37. | glide | move smoothly with little effort |
| 38. | hood | head covering for warmth |
| 39. | hook breathing | quick recovery breaths after surfacing |
| 40. | hydration | having enough body water |
| 41. | hypercapnia | excess carbon dioxide level |
| 42. | hyperventilation | overbreathing before a dive |
| 43. | hypoxia | dangerously low oxygen level |
| 44. | inhale | breathe air in |
| 45. | kelp | large brown seaweed |
| 46. | kick | propel with the legs |
| 47. | lanyard | safety tether to the line |
| 48. | lead | metal used for weighting |
| 49. | line | rope used for descent |
| 50. | lung packing | glossopharyngeal air loading |
| 51. | mammalian dive reflex | automatic diving body response |
| 52. | mask | face gear for underwater vision |
| 53. | middle ear | air space behind eardrum |
| 54. | monofin | single-blade fin for both feet |
| 55. | mouthfill | air held for deep equalizing |
| 56. | neckweight | weight worn around neck |
| 57. | negative | naturally sinking downward |
| 58. | neoprene | rubber used in wetsuits |
| 59. | neutral | neither sinking nor floating |
| 60. | no limits | sled descent and lift ascent |
| 61. | nose clip | device pinching the nose |
| 62. | O2 | oxygen in the body |
| 63. | OK | signal that all is well |
| 64. | open water | unconfined natural water area |
| 65. | packing | force extra air into lungs |
| 66. | positive | naturally floating upward |
| 67. | pressure | force exerted by surrounding water |
| 68. | protocol | standard safety procedure |
| 69. | pull | use arms on the line |
| 70. | purge | clear water from snorkel |
| 71. | recovery | breathing after surfacing |
| 72. | red card | disqualified competition dive signal |
| 73. | reef | ridge of rock or coral |
| 74. | rescue | assist a diver in trouble |
| 75. | reverse block | trapped expanding air on ascent |
| 76. | ribcage | bony chest structure |
| 77. | seal | watertight fit against skin |
| 78. | sinus | air cavity in the face |
| 79. | snorkel | tube for breathing at surface |
| 80. | squeeze | pressure injury from unequalized spaces |
| 81. | static | breath-hold without swimming |
| 82. | stiffness | how rigid a fin feels |
| 83. | streamline | reduce drag with body position |
| 84. | surge | back-and-forth water movement |
| 85. | tag | proof marker brought to surface |
| 86. | technique | method of performing a skill |
| 87. | thermocline | layer with temperature change |
| 88. | training | practice to improve ability |
| 89. | trim | balanced body position in water |
| 90. | turn | direction change at depth |
| 91. | urge | need to breathe |
| 92. | Valsalva | equalization by blowing gently |
| 93. | variable weight | descent aided by weighted sled |
| 94. | vasoconstriction | narrowing of blood vessels |
| 95. | visibility | how far one can see |
| 96. | visualization | mental rehearsal of a dive |
| 97. | weightbelt | belt carrying dive weights |
| 98. | wetsuit | insulating neoprene dive suit |
| 99. | white card | valid competition dive signal |
| 100. | wreck | sunken ship or structure |