In Section 2 of PADI’s Open Water Diver eLearning (Chapter 2 of the PADI Open Water Diver Manual), you have learnt some important concepts about being a diver, equipment handling, as well as scuba diving skills.
The PADI Open Water knowledge review section at the end of the second Chapter of your Manual (or eLearning section 2) will test your knowledge about seeing and hearing as a diver, swimming and moving, staying warm, breathing effectively underwater, ascents and descents in open water, and exposure suits.
Being knowledgeable with those concepts will help you become a good diver and get you ready for the open water diver “in-water” sessions.
If you are looking for explanations to other PADI Open Water knowledge review sections, check out the following links:
- PADI OWD Section 1 Knowledge Review Answers Explained
- PADI OWD Section 3 Knowledge Review Answers Explained
- PADI OWD Section 4 Knowledge Review Answers Explained
- PADI OWD Section 5 Knowledge Review Answers Explained
- PADI Open Water RDP Knowledge Review
- How to Use PADI Dive Tables
When I look at things underwater they often seem _______ than when I look at them on the surface.
Answer: When looking at things underwater, they often seem nearer and larger than when looking at them at the surface.
This is equally applicable to objects, people, and marine life.
In your open water manual, you have learnt that water is 800 times denser than air. This means that light rays change direction when passing from the water into the air space in your mask.
This process is called refraction and it makes objects seem bigger underwater by approximately 1/3 of their actual size.
If you have ever done some snorkelling, I can bet you have already found yourself in a situation where you were trying to reach an object like a coloured stone underwater but missed it by a couple of inches.
This is exactly because the object seemed closer and bigger than it actually was.
Sound travels well in water, and it is difficult to tell
Answer: Sounds travels well in water, and it is difficult to tell where it is coming from.
The speed of sound in air is about 1,125 ft/s (343 m/s; 1,235 km/h; 767 mph; 667 kn). Speed of sound in water is four times faster than air.
While at the surface, the way our brain tells the direction of sound, is by analysing the way sound reaches each single ear. Usually, sound reaches our ears with an imperceptible time lag.
The time lag at which the sound reaches each single ear provides our brain with an approximation of the direction the sound is coming from.
Underwater, given that sound travels approximately four times faster than at surface, the time lag at which sound reaches our ears is almost non-existent.
This is why is very difficult to tell the direction of sound underwater.
If I get cold while scuba diving and I can’t stop shivering (shaking), what should I do?
Answer: stop diving immediately, get out of the water, dry off and change into something warm.
As you will recall from your eLearning or from the Open Water manual, shivering is one of the first signs of hypothermia.
If possible and if required, you should still be doing the safety stop of 3 minutes at 5 meters depth without forgetting to control your ascent rate on your computer.
Starting to swim faster would only make you feel tired, worsen your gas consumption, and possibly lead to overexertion.
In sum, if you try to heat up your body underwater other than by aborting the dive, you are likely to end up in a worse situation than hypothermia.
Note that the same procedure applies whether you are diving in wet or dry suit, doing a boat or shore dive.
Learning when is a good moment to abort a dive is an essential concept in diving, and you are the only responsible to make such call.
The dive will be easier, I will use less air and I will get less tired, if I…
Answer: Move slowly and steadily.
One of our main objectives while scuba diving is to optimize gas consumption. Optimizing gas consumption makes it possible to have longer dives and enjoy more this amazing activity.
The best possible way to optimize gas consumption is to avoid wasting energy.
Energy, while scuba diving, is most commonly wasted by not having the proper exposure, by not being properly weighted and streamlined, or by moving too fast underwater.
In other words, having the proper trim and buoyancy while moving slowly and steadily will help you improve your dives both in terms of time underwater and fatigue.
When breathing underwater while scuba diving, I should
Answer: use airway control and breathe slowly, deeply and continuously (always breathe, never hold my breath).
One of the fundamental rules of scuba diving, as you have learnt in chapter 1 of the Open Water manual (section 1 of the eLearning) is to never hold your breath.
To avoid getting intoxicated and to optimize gas consumption and exchange, you should be breathing slowly and deeply.
This kind of breathing is often called “belly breathing” and is very similar to the way new-borns breathe.
You can exercise belly breathing also at the surface by placing one hand on your belly and feeling it moving while doing deep breaths.
Note that this procedure applies irrespective of the gas mixture you are breathing. For example, if you decide to continue with your diving education and take the enriched air diver exam and nitrox certification, you will learn that your way of breathing underwater should not change as you change gas mixtures.
A properly fitting wet suit keeps me warm by
Answer: reducing the amount of water moving in and out of my wetsuit.
A wet suit keeps a diver’s body warm by letting a small amount of water inside. Such small amount of water is then heated up with the diver’s body warmth and ideally remains at a constant temperature throughout the full duration of a dive.
Such process can only work if a wetsuit only allows a small amount of trapped water.
In fact, if you have a constant water inflow and outflow to and from your wetsuit, your body temperature will not be sufficient to warm up the water inside the wetsuit.
If you are interested in knowing how a wetsuit works, and how to choose the perfect scuba diving wetsuit, check out my ultimate guide on choosing the perfect scuba wetsuit. If instead you are wondering how a dry suit works, you can check out my ultimate guide. In either case your nearest PADI dive shop will surely be able to suggest the best exposure suit given your body shape.
If I experience overexertion, I should
Answer: stop all activity, signal my buddy and rest.
A diver that is overexerted underwater tends to have an irregular, accelerated breathing which in turn can lead to gas toxicity.
More precisely, overexertion whie scuba diving can lead to carbon dioxide poisoning, which in the most severe form may lead to nausea, vomiting, dizziness, flushing, confusion, and in some cases loss of consciousness.
If you experience over exertion, the most important action is to stop all activity, rest and conserve energy, while making sure that your buddy is keeping an eye on you.
This will also help you end the dive with enough air left in your cylinder.
The same procedure applies if you are diving nitrox (enriched air) or other gas mixtures instead of air.
If I am part of a three person dive buddy team and one of my buddies gets separated:
Answer: All three divers should enact the procedures for reuniting.
The logic behind this answer is quite straightforward. If you are diving in a buddy team of three person and one of the buddies gets separated, you should not take the risk of loosing an additional buddy.
This is why all divers should enact the buddy separation procedure for reuniting. Remember that unless specified differently by your diving instructor, you should not be looking for your byddy(ies) for more than a minute.
Being knowledreable with the PADI buddy system is key to scuba dive in safe conditions.
To control my buoyancy as I ascend after a dive, I should
Answer: Frequently release small amount of air from my BCD.
To understand this answer, think of the “balloon example”. If you inflate a balloon at depth and seal it, it will expand as it rushes to the surface. It will become more and more positively buoyant.
The only way to stop the balloon would be by slowly deflating it so that it could become neutrally buoyant and make a controlled ascent.
Your BCD works exactly like the balloon we have just seen. As you ascend, towards the end of a dive, it will inflate and eventually tend to pull you towards the surface.
How can I stay with my buddy on a scuba dive?
Answer: Decide who will lead the dive, which side of the leader I will be on, and where we are going to go.
In order to stay close to your buddy during a dive, it is essential to plan your dive before even getting into the water.
Elements you should consider while planning a dive are who will lead the dive, how you will be positioned relative to each other, which direction you will be taking and for how long, under what conditions you should turn the dive.
I strongly suggest you also refresh the buddy separation procedure to make sure you know how to behave in case one of you gets lost.