SDI SCUBA DIVER CERTIFICATION STUDY
GUIDE 2026/2027 – AUTHENTIC QUESTIONS
AND 100% VERIFIED CORRECT ANSWERS
EDITION.
◎ Color absorption with depth. ANSWER:- Water absorbs color starting with reds and
moving through the spectrum.
◎ Sound travel underwater. ANSWER:- Moves four times faster than in air, making
direction difficult to determine.
◎ Heat conduction in water. ANSWER:- Water conducts heat away from the body 25
times faster than air.
◎ Thermocline. ANSWER:- The boundary layer between different water temperatures.
◎ Primary cause of waves. ANSWER:- Wind.
◎ Rip current escape method. ANSWER:- Swim perpendicular to the current (parallel
to the shore).
◎ Surge. ANSWER:- The back-and-forth movement of water caused by overhead
waves.
◎ Most common aquatic life injuries. ANSWER:- Scrapes and abrasions, usually
caused by diver carelessness.
◎ Nematocysts. ANSWER:- Stinging cells possessed by animals like jellyfish and fire
coral.
◎ Ambient pressure increase rate. ANSWER:- Increases by 1 atmosphere (1 bar) for
every 10 m (33 ft) of descent.
◎ Gas volume vs. depth. ANSWER:- Volume is inversely proportional to pressure (half
volume at 10 m/33 ft).
◎ Gas density and air consumption. ANSWER:- Directly proportional to pressure; you
consume 3x more air at 20 m (66 ft).
◎ Preventing ear squeeze. ANSWER:- Equalize early and often during descent.
GUIDE 2026/2027 – AUTHENTIC QUESTIONS
AND 100% VERIFIED CORRECT ANSWERS
EDITION.
◎ Color absorption with depth. ANSWER:- Water absorbs color starting with reds and
moving through the spectrum.
◎ Sound travel underwater. ANSWER:- Moves four times faster than in air, making
direction difficult to determine.
◎ Heat conduction in water. ANSWER:- Water conducts heat away from the body 25
times faster than air.
◎ Thermocline. ANSWER:- The boundary layer between different water temperatures.
◎ Primary cause of waves. ANSWER:- Wind.
◎ Rip current escape method. ANSWER:- Swim perpendicular to the current (parallel
to the shore).
◎ Surge. ANSWER:- The back-and-forth movement of water caused by overhead
waves.
◎ Most common aquatic life injuries. ANSWER:- Scrapes and abrasions, usually
caused by diver carelessness.
◎ Nematocysts. ANSWER:- Stinging cells possessed by animals like jellyfish and fire
coral.
◎ Ambient pressure increase rate. ANSWER:- Increases by 1 atmosphere (1 bar) for
every 10 m (33 ft) of descent.
◎ Gas volume vs. depth. ANSWER:- Volume is inversely proportional to pressure (half
volume at 10 m/33 ft).
◎ Gas density and air consumption. ANSWER:- Directly proportional to pressure; you
consume 3x more air at 20 m (66 ft).
◎ Preventing ear squeeze. ANSWER:- Equalize early and often during descent.
