Free Open Water Scuba Practice Exam

Q: Is this the real PADI / SSI / NAUI exam?

No. Every question is original, written to mirror the format, difficulty and reasoning of the entry-level Open Water written exam without copying any agency's copyrighted test. Because all agencies test the same core theory, it prepares you for PADI, SSI and NAUI.

Q: How many questions are on the Open Water exam?

The entry-level Open Water written exam is typically 50 multiple-choice questions with a pass mark around 75%. This free practice exam matches that: 50 questions across physics, equipment, physiology, planning, safety and the environment.

Q: Is this practice exam really free?

Yes — all 50 questions are free, with instant scoring, an explanation for every answer, and a topic-by-topic breakdown. No signup required to take it.

Question 1

A flexible balloon of air is taken from the surface down to 10 m (33 ft). Its volume becomes:

Accepted Answer

Half as large — Pressure doubles from the surface (1 ata) to 10 m (2 ata), so by Boyle's law the air volume is halved. This is why air spaces compress on descent.

Answer

Twice as large

Answer

Unchanged

Answer

A quarter as large

Question 2

What is the total (absolute) pressure at 30 m / 99 ft of seawater?

Accepted Answer

4 ata — Pressure rises 1 atmosphere every 10 m, plus 1 at the surface: 30 m = 3 (from depth) + 1 = 4 ata.

Answer

3 ata

Answer

30 ata

Answer

1 ata

Question 3

Why do you use air from your tank faster as you go deeper?

Accepted Answer

The gas you breathe is denser, so each breath contains more air — Under higher pressure the breathing gas is compressed and denser, so every breath drains more of your supply. At 20 m you use air roughly three times faster than at the surface.

Answer

The tank shrinks

Answer

Your lungs get bigger

Answer

The regulator leaks at depth

Question 4

As you descend, a diver's mask can press against the face. This is caused by:

Accepted Answer

The air inside the mask compressing (Boyle's law) — The air in the mask compresses with depth, creating 'mask squeeze'. You equalize it by exhaling gently through your nose into the mask.

Answer

Cold water

Answer

Salt buildup

Answer

A faulty strap

Question 5

Which colour disappears first as you descend?

Accepted Answer

Red — Water absorbs longer wavelengths first, so red fades within the first ~5 m, followed by orange and yellow. That's why deep scenes look blue-green without a light.

Answer

Blue

Answer

Green

Answer

Black

Question 6

Objects underwater appear:

Accepted Answer

Larger and closer than they really are — Refraction through your mask magnifies things by about 33%, making objects look larger and closer than they actually are.

Answer

Smaller and farther away

Answer

Exactly their true size

Answer

Upside down

Question 7

What is the main purpose of a BCD (buoyancy control device)?

Accepted Answer

To add or release air so you can control buoyancy — The BCD lets you fine-tune buoyancy — add air to float, release it to descend — and hold you comfortably at the surface.

Answer

To store your air

Answer

To keep you warm

Answer

To measure depth

Question 8

A submersible pressure gauge (SPG) tells you:

Accepted Answer

How much air remains in your tank — The SPG shows remaining tank pressure (bar or psi). Checking it regularly and surfacing with a reserve is core gas management.

Answer

Your depth

Answer

The water temperature

Answer

Your ascent rate

Question 9

The primary job of a scuba regulator is to:

Accepted Answer

Reduce high tank pressure to a pressure you can breathe — A regulator steps high-pressure tank air down to ambient pressure so you can breathe it easily and comfortably at any depth.

Answer

Warm the air you breathe

Answer

Filter salt from the water

Answer

Inflate your BCD automatically

Question 10

The alternate air source (octopus) exists mainly to:

Accepted Answer

Let you or your buddy share air in an emergency — The octopus is a second second-stage so you can donate air to an out-of-air buddy and ascend together safely.

Answer

Breathe through your nose

Answer

Store spare weights

Answer

Clean your mask

Question 11

A wetsuit keeps you warm by:

Accepted Answer

Trapping a thin layer of water your body heats — A wetsuit traps a thin layer of water against your skin; your body warms it, and the neoprene slows heat loss. It is not meant to keep you dry.

Answer

Keeping you completely dry

Answer

Generating heat electrically

Answer

Reflecting sunlight

Question 12

To check a new mask stops fogging, before first use you should:

Accepted Answer

Scrub the lens to remove the factory film, then apply anti-fog — New lenses carry a manufacturing film that causes fog. Scrub the inside once (toothpaste or mask cleaner), then use anti-fog before each dive.

Answer

Freeze it overnight

Answer

Rinse it in hot water only

Answer

Never touch the lens

Question 13

What does a dive computer continuously track for you?

Accepted Answer

Depth, dive time and your remaining no-stop limit — A dive computer monitors depth and time in real time and calculates your remaining no-decompression limit, updating as your dive changes.

Answer

Only the time of day

Answer

Water salinity

Answer

Your heart rate

Question 14

When should you equalize your ears on descent?

Accepted Answer

Early and often, before any discomfort — Equalize early and often — start at the surface and repeat every metre, before you feel pressure. Waiting until it hurts can make the ear hard to clear.

Answer

Only once you feel pain

Answer

Just once at the bottom

Answer

Only if water is cold

Question 15

Why must you never hold your breath while scuba diving?

Accepted Answer

The air in your lungs expands on ascent and can injure them — As you ascend, pressure drops and lung air expands. Holding it can over-expand and rupture lung tissue (a lung-over-expansion injury). Breathe continuously at all times.

Answer

It wastes air

Answer

It fogs your mask

Answer

It makes you sink

Question 16

Decompression sickness (DCS) is caused by:

Accepted Answer

Nitrogen coming out of solution as bubbles after ascending too fast or exceeding limits — Absorbed nitrogen forms bubbles in tissue and blood when you ascend too quickly or exceed your no-stop limit. Slow ascents and safety stops prevent it.

Answer

Drinking seawater

Answer

Cold water on the skin

Answer

Breathing too slowly

Question 17

The first aid for a diver with suspected decompression sickness is to:

Accepted Answer

Give 100% oxygen and seek emergency medical care — Administer 100% oxygen and arrange emergency care; definitive treatment is a hyperbaric (recompression) chamber. Never send a suspected DCS diver back down.

Answer

Have them hold their breath

Answer

Send them back underwater

Answer

Give them a cold drink

Question 18

Nitrogen narcosis is best relieved by:

Accepted Answer

Ascending to a shallower depth — Narcosis is reversible — ascending a few metres clears it within minutes. It comes from breathing nitrogen under pressure, usually below about 30 m.

Answer

Descending deeper

Answer

Holding your breath

Answer

Removing your regulator

Question 19

Breathing slowly and deeply while diving mainly helps by:

Accepted Answer

Conserving air and preventing carbon-dioxide buildup — Slow, deep breaths use gas efficiently and clear CO₂, which otherwise causes headaches, shortness of breath and panic. Never skip-breathe to save air.

Answer

Making you sink

Answer

Warming the tank

Answer

Speeding your ascent

Question 20

Which of these increases your risk of decompression sickness?

Accepted Answer

Dehydration, cold and hard exertion — Dehydration, cold and heavy exertion all raise DCS risk. Stay hydrated, dive within limits, and add conservatism for cold or strenuous dives.

Answer

Staying well hydrated

Answer

Ascending slowly

Answer

Making a safety stop

Question 21

Barotrauma is an injury caused by:

Accepted Answer

Pressure differences in the body's air spaces — Barotrauma is pressure-related injury to air spaces — ears, sinuses, lungs, mask or teeth — when they can't equalize. Equalizing early and never holding your breath prevents it.

Answer

Marine life stings

Answer

Too much sunlight

Answer

Salt in the eyes

Question 22

What happens to your no-decompression limit as you go deeper?

Accepted Answer

It gets shorter — Deeper means faster nitrogen absorption, so your no-decompression limit gets shorter — long in shallow water, very short near recreational depth limits.

Answer

It gets longer

Answer

It stays the same

Answer

It disappears

Question 23

A standard safety stop is approximately:

Accepted Answer

3 minutes at 5 m (15 ft) — A safety stop is about 3 minutes at 5 m (15 ft), made near the end of a dive to let extra nitrogen off-gas before surfacing.

Answer

1 minute at 10 m

Answer

5 minutes at 20 m

Answer

10 minutes at the surface

Question 24

The maximum ascent rate recommended for recreational diving is about:

Accepted Answer

18 m / 60 ft per minute or slower — Ascend no faster than 18 m / 60 ft per minute — slower is better. A fast ascent doesn't let nitrogen off-gas and risks decompression sickness.

Answer

No limit — ascend as fast as you like

Answer

50 m per minute

Answer

1 m per hour

Question 25

Compared with air, nitrox (enriched air) mainly lets you:

Accepted Answer

Stay longer at recreational depths — Nitrox has less nitrogen, extending your no-decompression limits (more bottom time). Because of the extra oxygen it has a shallower maximum depth, not a deeper one.

Answer

Dive much deeper

Answer

Skip safety stops

Answer

Breathe less often

Question 26

The generally accepted maximum depth for recreational diving is:

Accepted Answer

40 m / 130 ft — Recreational diving is limited to 40 m / 130 ft. New Open Water divers are typically limited to 18 m / 60 ft until further training.

Answer

10 m / 33 ft

Answer

100 m / 330 ft

Answer

There is no limit

Question 27

A second dive right after a first one has a shorter no-stop limit because:

Accepted Answer

Residual nitrogen is still in your body from the first dive — You still carry residual nitrogen from the first dive, so a repetitive dive starts with less available no-stop time. A longer surface interval off-gases more.

Answer

The tank is colder

Answer

The water is deeper

Answer

Your computer resets

Question 28

When planning a multi-level dive, you should generally:

Accepted Answer

Do the deepest part first, then work shallower — Plan the deepest portion first and progressively move shallower. This manages nitrogen loading more safely than descending again late in the dive.

Answer

Do the shallowest part first

Answer

Stay at one depth the whole time

Answer

Go up and down repeatedly

Question 29

If your dive computer and a dive table disagree on your limit, you should:

Accepted Answer

Follow the more conservative (shorter) limit — Always follow the more conservative number. When in doubt, less bottom time and a slower ascent are the safer choice.

Answer

Average the two

Answer

Ignore both

Answer

Follow whichever is longer

Question 30

Your buddy signals they are out of air. What do you do first?

Accepted Answer

Offer your alternate air source (octopus) — Donate your alternate air source so your buddy can breathe, then ascend together slowly. The buddy system exists for exactly this.

Answer

Race to the surface alone

Answer

Take a photo

Answer

Drop your weights

Question 31

Underwater, a 'thumbs-up' signal means:

Accepted Answer

Let's go up / end the dive — Thumbs-up means 'go up / end the dive'. To say you're fine, use the finger-and-thumb 'OK' circle — mixing these up is a classic mistake.

Answer

I'm OK / everything's good

Answer

Look over there

Answer

I'm low on air

Question 32

The correct way to signal 'OK' underwater is:

Accepted Answer

A thumb-and-forefinger circle — 'OK' is a circle made with thumb and forefinger, used both to ask 'are you OK?' and to answer 'I'm OK'. A thumbs-up would mean ascend.

Answer

A thumbs-up

Answer

A closed fist

Answer

A wave

Question 33

The pre-dive safety check with your buddy (PADI) is remembered as:

Accepted Answer

BWRAF — BWRAF — BCD, Weights, Releases, Air, Final check. A quick buddy check before every dive catches problems while you can still fix them.

Answer

ABCDE

Answer

SCUBA

Answer

PADI

Question 34

To clear a flooded mask underwater, you:

Accepted Answer

Look up slightly, press the top of the frame, and exhale through your nose — Tilt your head up a little, press the top of the mask against your forehead, and breathe out through your nose to push the water out the bottom.

Answer

Hold your breath and squint

Answer

Rip the mask off

Answer

Swim to the surface immediately

Question 35

If you become separated from your buddy underwater, you should:

Accepted Answer

Search for about one minute, then surface to reunite — Look around for roughly a minute; if you don't find them, ascend slowly and safely to reunite at the surface. Agree this plan before the dive.

Answer

Keep diving alone

Answer

Descend deeper to look

Answer

Wait on the bottom until they find you

Question 36

You should surface from a dive with a reserve of about:

Accepted Answer

50 bar / 500 psi — Plan to reach the surface with roughly 50 bar / 500 psi in reserve. Monitor your SPG and begin your ascent in good time, not when the tank is empty.

Answer

0 bar / 0 psi

Answer

Full tank pressure

Answer

It doesn't matter

Question 37

Hours after a dive you feel unusual joint pain and fatigue. You should:

Accepted Answer

Treat it as possible DCS: get oxygen and seek medical help — Delayed joint pain and fatigue can be decompression sickness. Don't dismiss it — breathe oxygen if available and seek medical advice promptly.

Answer

Ignore it — it always passes

Answer

Go for another dive

Answer

Take a hot shower and sleep

Question 38

Neutral buoyancy means you:

Accepted Answer

Hover without rising or sinking — Neutral buoyancy is the balanced state where you neither rise nor sink — you hover. Set it with your BCD and fine-tune with your breathing.

Answer

Float to the surface

Answer

Sink to the bottom

Answer

Spin in circles

Question 39

Good buoyancy control matters for the reef because:

Accepted Answer

It stops you crashing into or damaging fragile coral and marine life — Hovering with control keeps fins and gear off delicate coral and away from animals — protecting the environment and keeping you safe.

Answer

It looks impressive

Answer

It saves battery

Answer

It warms the water

Question 40

The general rule about touching marine life is:

Accepted Answer

Look but don't touch — Look but don't touch. Contact can harm animals, damage coral, and some marine life can sting or bite. Keep good buoyancy and stay off the bottom.

Answer

Touch anything colourful

Answer

Feed the fish snacks

Answer

Collect a souvenir

Question 41

On a drift dive you:

Accepted Answer

Move with the current while the boat follows your bubbles — In a drift dive you let the current carry you and the boat tracks your surface marker or bubbles. Fighting the current wastes air and energy.

Answer

Anchor yourself to the reef

Answer

Swim hard against the current the whole time

Answer

Stay perfectly still

Question 42

If a current is carrying you away from the boat at the surface, you should:

Accepted Answer

Establish buoyancy, signal, and don't exhaust yourself fighting it — Inflate your BCD for positive buoyancy, signal for attention, and avoid burning out against the current. Conserving energy and staying visible keeps you safe.

Answer

Swim straight against it until exhausted

Answer

Remove your fins

Answer

Dive back down immediately

Question 43

Cold water affects a dive by:

Accepted Answer

Increasing air consumption and the risk of getting chilled — Cold raises air consumption and can chill you, which also increases DCS risk. Dress for the temperature and add conservatism to your plan.

Answer

Reducing your air consumption

Answer

Making nitrogen harmless

Answer

Removing the need for a safety stop

Question 44

A common way to enter the water from a dive boat is the:

Accepted Answer

Giant stride or backward roll — The giant stride (from a stable platform) and the backward roll (from a small boat) are the standard entries — one hand holding your mask and regulator in place.

Answer

Head-first dive

Answer

Cannonball

Answer

Ladder climb-down only

Question 45

Before descending on any dive, a key part of your buddy plan is to:

Accepted Answer

Agree maximum depth, time and hand signals — Plan your dive and dive your plan: agree your maximum depth and time, turn-around pressure, signals and what to do if separated — before you go under.

Answer

Race each other down

Answer

Turn off your computers

Answer

Remove your weights

Question 46

Why should a newly certified Open Water diver not exceed 18 m / 60 ft?

Accepted Answer

It's the depth their training and experience prepared them for — 18 m / 60 ft matches an Open Water diver's training and experience. Going deeper (to the 40 m recreational limit) needs further training such as Advanced Open Water.

Answer

The water is too cold below that

Answer

Fish don't live deeper

Answer

Tanks stop working

Question 47

A reverse block is:

Accepted Answer

Expanding air trapped in an air space that can't escape on ascent — On ascent, air in the ears, sinuses or a tooth can expand and become trapped, causing pain. Slow down or stop your ascent to let it equalize gradually.

Answer

A weight that won't release

Answer

A tangled BCD hose

Answer

A frozen regulator

Free Open Water scuba practice exam

A flexible balloon of air is taken from the surface down to 10 m (33 ft). Its volume becomes:

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