15 questions modeled on the Open Water Diver final exam. Answer all 15, then get your score with a full explanation for every answer — no account needed.
1What is a key reason to stay well hydrated before diving?
Why: Good hydration helps the body off-gas nitrogen and lowers the risk of decompression sickness.
2Which statement about the out-of-air signal is correct?
Why: The signal is a flat hand moved across the throat, and the correct buddy response is to donate an alternate air source.
3Why should an Open Water Diver stay within 18 metres (60 feet) rather than going deeper?
Why: Open Water Diver training and experience are matched to depths up to 18 metres; going deeper increases risks the diver has not yet been trained to manage.
4The regulator reduces the ______ pressure of the cylinder air to a comfortable pressure for breathing.
Why: Cylinder air is stored at very high pressure; the regulator reduces this high pressure for comfortable breathing.
5If sound travels roughly four times faster in water than in air, what practical effect does this have for a diver?
Why: Because sound arrives at both ears almost simultaneously, a diver finds it very hard to determine the direction of a sound source.
6At what depth in seawater is a diver exposed to a total (absolute) pressure of 2 bar/ata?
Why: Pressure increases by 1 bar for every 10 m of seawater. At the surface it is 1 ata; 10 m adds 1 more, giving 2 ata.
7After a dive, your buddy reports numbness and unusual fatigue. What should you do?
Why: Suspect decompression sickness. Have them breathe emergency oxygen and activate the emergency medical system so they can receive professional evaluation and treatment.
8You get a cramp in your calf muscle while diving. What is the recommended response?
Why: Stop finning and gently stretch the cramped muscle, for example by pulling the fin tip toward you to extend the calf, until the cramp eases.
9On a repetitive dive, why must the residual nitrogen from the previous dive be accounted for?
Why: Because leftover nitrogen adds to the nitrogen absorbed on the next dive, the diver reaches the no-decompression limit sooner, so allowable bottom time is reduced.
10Why does adding a wetsuit usually require a diver to carry more weight?
Why: Neoprene contains gas bubbles that make it buoyant, so the extra buoyancy of a thicker suit must be offset with additional lead to achieve neutral buoyancy.
11Which statement about a wetsuit-clad diver descending is correct?
Why: As pressure rises the neoprene and BCD air compress, buoyancy is lost, and the diver adds air to the BCD to stay neutral.
12According to Boyle's Law, what happens to the volume of a flexible air space as a diver descends?
Why: Boyle's Law: at constant temperature, volume is inversely proportional to pressure. Descending raises pressure, so volume decreases.
13When should you begin equalising your ears on a descent?
Why: Equalise early and often, before you feel discomfort. Gently pinch the nose and blow, or swallow, starting at the surface and every metre or so as you go down.
14You are out of air at 8 metres, your buddy has drifted out of reach, and the surface is clear above you. What is your best option?
Why: With no buddy in reach and a shallow depth, perform a controlled emergency swimming ascent, exhaling continuously as you swim to the surface.
15A widely used memory aid for the pre-dive buddy check covers, in order, roughly:
Why: A common sequence checks BCD/buoyancy, weights/releases, releases/clips, air/regulators, and a final gear/go review.
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These 15 questions are modeled on the 50-question Open Water Diver final exam (you need 75% to pass). They're original questions covering the real topics and difficulty — not the certifying agency's actual test. For unlimited fresh questions, per-topic drills, and full-length mock exams, read the Open Water Diver exam guide or create an account for unlimited practice.
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