Scuba Diving Technical Questions

Scuba Diving Technical Questions Answered

Why are ice divers tethered?

Ice divers need to be tethered for safety. Every diver must wear a harness under their scuba suit that a line is secured to. The other end is secured by various methods. Because ice diving only allows for one entry/exit point, it is crucial that divers can find their way back to this hole when needed.

What are the three primary areas that are focused on in ice diving training?

  1. How to correctly handle a frozen air-supply situation by using a backup system.

  2. How to properly make impact with the underside of the ice surface if your weight belt falls off and you ascend rapidly and uncontrollably.

  3. What to do if a diver does not give feedback on the line or somehow loses contact.

In ice diving, why is the harness worn underneath the buoyancy device?

The harness is put on over your wetsuit yet under your buoyancy device so even if you have to remove your buoyancy device or air cylinder, you are still tethered to the line. The harness is worn around the back and over the shoulders so that an unconscious diver can be pulled safely back to the hole.

How many divers should dive simultaneously from one hole while ice diving?

A maximum of two divers can dive in one hole at the same time with their own rope. Traditionally, two divers won't get their ropes tangled but a third diver would significantly increase this risk.

How can you preheat your suit before an ice dive?

Your suit is easily preheated by simply pouring warm water on it.

What are the four main rope signals used in an ice dive from tender to diver?

  1. One pull asks if the diver is okay.

  2. Two pulls tells the diver to stop, take out slack or reverse direction.

  3. Three pulls tells the diver to come to the surface.

  4. Four pulls lets the diver know to immediately stop and don't move, there could be danger.

What are the four main rope signals that are used in a cave dive from diver to tender

  1. One pull signals that the diver is okay.

  2. Two pulls asks for an advance in the line.

  3. Three pulls lets the tender know that an object has been found.

  4. Four pulls asks for assistance.

Why is cave diving training done in segments?

Cave diving is typically taught in segments with each additional one becoming more complex. It is important that every segment be coupled with an adequate amount of experience before continuing to a more advanced level. Academic training where cave diving is concerned is not enough to be able to handle an underwater emergency. It requires hands-on learning after every segment for a diver to be confident enough to remain calm if a problem arises.

What is the number one cause of fatalities in cave diving and how can these be prevented?

Failing to use a guide line causes the highest fatality among non-certified, untrained divers. A continuous guide line should always be maintained between the dive team and the leader and a fixed point should be selected in open water outside of the cave. For extra safety measures, the line should be tied off again right inside the cavern zone as a backup. There should always be adequate tension on the line so that a diver can find their way out of the cave entrance should a silt out happen.

Why should cave divers not dive to an excessive depth like open water divers can?

As a rule, decompression obligation and gas consumption increases with depth. It is vital that divers do not exceed their dive plan as well as their maximum operating depth of gas mixture used. Additionally, in a cave, nitrogen narcosis effects are higher than a diver who is at an identical dept in open water. Not paying close attention to depth is a huge cause of cave diving fatalities.

What is the “rule of thirds” in cave diving?

The rule of thirds states that the initial air supply is divided equally into thirds and split between ingress, egress and emergency support for a team member. This rule was originally devised as a safe approach to diving the caves in Florida since they have high outflow currents. This reduces air consumption where the diver is exiting. A cave system that has little outflow requires that more air be reserved for the exit.

How many lights are required for cave divers?

Cave divers are required to have three independent light sources. One is primary while the other two are for backup use. In the case that one light happens to fail for a diver, all members of the team must end the dive.

What are the basic skills needed for a new diver cave diving with a certified buddy?

Cave diving training basics include propulsion techniques, reel and handling, gas planning and communication. Once a diver is introduction certified, cave dive distances can be gradually increased every time.

What does apprentice cave diving training cover?

Apprentice training acts like a building block to penetrate caves deeper. Decompression procedures and complex dive planning for longer dives are learned. An apprentice diver has usually one year to complete a full cave or this stage in training has to be repeated.

What is a diver able to do after full cave training is complete?

A diver who has completed full cave training can penetrate caves very deep working from permanent guidelines and sidelines. They can plan longer and more complex dives by using decompression and they are allowed to complete multiple gaps or jumps during the dive.

What does a station refer to in cave diving?

A station is the location where the line is in direct contact with the diving environment. This visually occurs wherever a passage distinctly changes in direction or depth. A station is in the form of tie-off or placement.

What is the difference between a tie-off or placement in cave diving?

When the line rests passively on a wall, it is considered a placement. These are ideal for navigation in non-critical areas but are not as effective in some circumstances since the line can be pulled because there is no anchoring point.

A line that is attached to an object is a tie-off and these have to be used in critical areas. To properly tie-off, you wrap the line around an object twice and lock it by looping the reel either under or over the line and then pulling it tight.

What dangers do you need to be aware of when cave diving?

Cave diving is dangerous and challenging if you aren't educated on the potential dangers. Since you cannot surface directly, you may have to swim a substantial distance to escape the cave so you always must be aware of how much air that you have left.

Visibility can be low and sometimes non-existent from lack of natural light and caves will often contain, mud, sand, silt or clay that you need to be careful to not stir up or visibility can be decreased even more.

Caves often carry extremely strong currents, emerging as either siphons or springs on the surface. These can cause serious problems if not managed correctly.

How is a light signal used in cave diving?

A primary light is used for communication. Making a circle with the light signals a newly made tie-off. This ensures that everyone on the team agrees on the route and that they are all okay.

Who has the right of way on a cave dive when encountering another team?

In the even that two teams meet, the team that is exiting always has the right of way because chances are, they have a lot less air left. Never shine your light in the direction of approaching divers.

What are the three biggest concerns to be aware of in altitude diving?

With the increased depth of an altitude dive, hypoxia, hypothermia and decompression sickness are all major concerns.

What are the three most important equipment considerations to be aware of on an altitude dive?

  1. Buoyancy – At altitude, the air that is trapped in the cells of your wetsuit expand and make you more buoyant. Always complete a buoyancy check.

  2. Gauges – Some gauges can act differently at altitude. Always be familiar with your gauges and if they are affected by altitude.

  3. Computer – Either your computer will need to be manually adjusted or it will adjust itself with altitude. Know your computer!

What is the safe rate to ascend on an altitude dive?

30 ft per minute is the maximum rate you can ascend on an altitude dive and safety stops are mandatory.

How long should you wait after arrival at a location before participating in an altitude dive?

It is suggested by the United States Navy to wait 12 hours so that you can adjust to the altitude.

How does freshwater and seawater influence an altitude dive?

Most altitude dives are carried out in freshwater which has a significantly lower density than seawater. Adjustments need to be considered when calculating decompression labels based on the body of water.

Why should a cutting device be carried on wreck dives?

Many well preserved or attractive wrecks are in deeper water, adding more precautions. Wrecks are quite often snagged by nets or fishing lines so a cutting device is crucial in case the diver becomes tangled up in a line.

What is progressive penetration in wreck diving?

Progressive penetration takes the place of reels. The diver completes several successive penetrations with each one a little deeper than the last. The diver has to memorize the inward and outward journeys. Three lights are always required.

What is the frog kick?

The frog kick is a type of swimming action that is used when you are near a silty seabed that could reduce visibility if stirred up. This is usually used in wreck diving and cave diving.

How does Nitrox decrease risks for decompression sickness?

Scuba diving primarily uses enriched air nitrox with a minimum of 21 percent oxygen content. By increasing oxygen proportions and decreasing nitrogen proportions, decompression sickness risks are reduced. This allows for longer dives with less decompression stops.

How do divers determine decompression requirements?

An equivalent air depth can be manually calculated or divers may use nitrox-capable dive computers or nitrox tables to determine decompression requirements.

How can divers avoid hypoxia on deep technical dives?

Hypoxia gases are typically breathed in at the bottom of deep technical dives. To avoid hypoxia, a diver may breath in a “travel mix” of a nitrox mix containing less that 50 percent of oxygen at the start of their descent.

What information should be found on the tag of every nitrox cylinder?

Nitrox cylinders should display a tag with the oxygen content, the gas blender's name, the date that it was blended and maximum operating depths as well as what pressure that the depth was calculated with.

What are vital components to diving with nitrox?

Buoyancy control is the most important element that a diver must excel at to dive with nitrox safely as well as a disciplined approach to planning, preparing and executing their dive. It is important that divers never exceed the maximum operating depth that they plan their dive for.

What does VENTID-C stand for?

Divers using nitrox use the word VENTID-C to be aware of the symptoms of oxygen toxicity. It stands for vision, ears, nausea, twitching, irritability, dizziness and convulsions. The vision relates to any blurriness while the ears questions any ringing. However, this cannot be solely relied on because many non-fatal convulsions offer evidence that there were no prior symptoms present.

What precautionary fill station procedures must be followed for a nitrox dive?

The oxygen percentage of every nitrox cylinder should be personally checked by the dive. If there is more than a one percent deviation, the diver needs to either recalculate or abort the dive. Around the world, dive resorts require that nitrox cylinders must be personally signed out in a log book with the cylinder number, signature of the diver, measured oxygen, percent composition and the cylinder's maximum operating depth.

What four gases can be used on a technical mixed gas dive?

While nitrox is used mainly for recreation dives, hydrox, heliair, heliox and trimix are used on a lot of technical dives.

What does trimix consist of and what are the advantages?

Trimix is a type of breathing gas that is made up of oxygen, nitrogen and helium. It allows a gas mix to be breathed in safely on deeper dives. Trimix reduces oxygen toxicity risks and has little narcotic effects. Helium leaves tissues fast due to its low molecular weight so it is not a heavy as nitrogen.

At what depth does nitrogen narcosis symptoms appear?

Divers will begin showing signs of nitrogen narcosis at 100 ft.

At what depth does a high risk of oxygen toxicity occur?

Compressed air results in oxygen toxicity at 218 ft.

What is the maximum depth that a diver can use trimix?

Trimix cannot be used by technical divers past 330 ft.

What are the three essential features that must be present to safely breathe gas?

  1. There must be enough oxygen present to support the breather.

  2. There must be no harmful gases present such as carbon dioxide or carbon monoxide.

  3. The gas that you are breathing must not become toxic under pressure.

What is subcutaneous emphysema?

This is when there is gas that is present beneath the skin, in the tissue.

Why is stretching first important in solo diving?

Stretching increases your flexibility and allows your muscles and joints to move better. It reduces your risk for cramps and increases your heart rate, breathing and blood flow. Stretching helps you manage your diving posture and remain safe and controlled which is vital when you are on your own.

What does the term shallow water blackout mean?

Shallow water blackout occurs when a diver loses consciousness during a breath-hold dive from lack of oxygen. This can actually occur at any depth but is most common during ascent.

What are the most common hand signals used in technical dives?

  • Thumbs up means let's go up.

  • Thumbs down means lets go done.

  • Creating a circle with the index finger and thumbs while allowing the fingers to stand up signals either “Are you okay?” or “I'm okay.”

  • Chopping the throat with a hand or tapping on the mouthpiece implies that the diver is out of air.

  • Wobbling a flat hand suggests a minor problem.

  • Creating an arc with the forearm signals an emergency.

  • Hugging the chest is a signal of being cold.

  • Indicating a rising and falling chest action with hands means that you are out of breath.

  • Clenching and unclenching your fist says that you have a cramp.

  • Shrugging your shoulders with palms facing up either means that you don't know, don't understand or you have a question.

  • Hand flat against chest or forehead is a signal for a shark.

  • Creating a wave motion with your hand across your torso represents a current.

  • Placing your hands flat on top of each other and waving thumbs means a large turtle is nearby.

  • Both fists placed against the head represents a hammerhead shark.

  • Covering your mouth with the back of your hand and wiggling all of your fingers signals an octopus in sight.

What are the three main flashlight or torch signals used in technical diving?

  1. Drawing a circle with the light on the ground signals OK.

  2. Waving the light vertically up and down signals that you want the other diver's attention.

  3. A rapid horizontal motion indicates an emergency.




Scuba Diving Technical Questions

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