2. Course Goals:
To learn the basic techniques, theory, and safety measures associated with breath hold
diving.
Objectives:
-Students will be able to demonstrate a working knowledge of Mammalian Dive
Reflex as it pertains to breath hold diving.
-Students will be able to perform the basic dive techniques: The diver’s breathe up,
initial dive, and a proper dive kick.
-Students will review and adhere to common sense dive safety rules and practices.
Enjoy!
3. What is free diving?
Also known as “apnea diving” or “breath hold diving,” free diving is
simply underwater swimming without the aid of SCUBA equipment.
Free diving has existed for millennia as a way for people to collect food
from the world’s oceans and other bodies of water. Today however, free
divers are mostly of the recreational and sport variety.
Free divers can reach impressive depths that would be difficult even
with SCUBA gear. The world record depth for a breath hold dive
currently stands at over 895 feet.
4. What do I need?
To start freediving, you do not need any gear at all. You simply need
yourself, and water deep enough to dive in. However, most free divers
dive with at least a mask, snorkel, and fins. Additional equipment can
include a wetsuit, weight belt, dive knife, diver’s buoy, and other gear.
How much gear you use is up to you.
For a beginner, I would recommend a simple mask/fin/snorkel setup like
you would buy for a snorkeling trip. A wetsuit and weight belt may also
be needed depending on your local water conditions.
5. Mammalian Dive Reflex
As humans, we are not born with fins, but we are born with the ability to
dive. This is because of Mammalian Dive Reflex.
All mammals are born with this reflex, which allows us to hold our breath
underwater longer than we would be able to out of water, as well as adapt to
depth pressure. In humans, the reflex can be achieved by immersing the face
in cool water.
The effects of this are:
-Decreased heart rate
-Decreased blood flow to extremities
-Release of extra oxygen rich red blood cells
-At depths of over 30 meters, we experience blood shift, in which plasma cells
fill the extra space in our lungs, keeping them from collapsing under pressure.
6. Review & discussion
What are the effects of mammalian dive
reflex on the human physiology? How are
these effects initiated?
What is blood shift? Do you think this
commonly experienced by recreational
divers?
Why do you think humans have
mammalian dive reflex?
7. To begin, we will start with the “breathe up.” The purpose of the breathe
Basic dive techniques
up is simple: To free the lungs and blood of excess CO2, and fill them
with as much oxygen as is possible without experiencing an oxygen
related blackout during the dive.
To maintain a safe dive, take no more than three to five deep breaths. If
you feel hyperventilated or dizzy AT ALL from your breathe up, you
should not commence the dive. Although hyperventilation can let you
stay underwater longer, it can also kill you as you may trick your body
into thinking it can stay underwater longer than it can. DO NOT put this
to the test, it is no joke- Even seasoned professional divers have lost
their lives trying to push the limits of a breathe up.
8. Try It!
Go ahead!
Take a deep breath, then hold your breath with a timer
running. How long did you last?
Catch your breath and try again, taking a diver’s breathe
up with 3 to 5 deep breaths. Did your breath hold last
longer?
Do you have a pool or water available? Try a third time
with the breath up, and with activating your dive reflex by
submerging your face in cool water. Is your time even
better?
9. Once you’re able to complete a safe and effective breathe
In the Water
up, it is time to hit the water. The first technique we’ll cover
is the initial dive. The purpose of the initial dive is to stack
your bodyweight over your head in a vertical pose, which will
drive you downwards, greatly reducing the effort required to
dive.
To perform an initial dive, start in a normal snorkeler’s
position (floating horizontally). Then, after getting a good
breath, kick one leg over your head while simultaneously
bending downward at the waist. Next, begin to kick your
other leg over your head (following the other) and straigten
out your body so you are facing directly down. If properly
executed, you should now be horizontal in the water, and
the shift of your body weight should drive you downwards to
depths of ten to twenty feet or so.
As you dive downwards, you will need to pressurize your
nasal cavity to avoid discomfort. This can be accomplished
easily by pinching your nose and gently “blowing” to
pressurize your ears (the same trick you would use in a
descending aircraft).
10. Once you have managed the initial dive, you’ll need to finish your descent, and then
Divers Kick
move about if you choose. To do this, you’ll need to learn a diver’s kick. “Kick” is
perhaps not the best word, because contrary to what the word implies, the diver’s kick
is a very subtle motion. Rather than thrashing your feet or fins wildly, your kick should
start as a gentle motion at the shoulders that travels down your entire body and ends
with your feet gently alternating. The purpose here is to move efficiently without using
up oxygen with unnecessary effort or forced motion.
QuickTime™ and a
decompressor
are needed to see this picture.
11. Safety!
When diving, safety is absolutely necessary. By not observing
Dive Buoy
common sense safety rules, you can end up seriously hurt, or Don’t Touch!
dead. Here are some basic rules to start with:
-Always, always, always, dive with a partner- And stick
with your partner. “One up, one down” is the rule, meaning that
both divers should never be underwater at the same time.
-Never dive in an area heavily trafficked by boats. If you
do dive in an area where boat traffic is possible, use a dive
buoy (with a flag) to alert boaters of your presence.
-Do not dive in bad weather, you will not be able to see, it Watch out for propellers!
will be dangerous, and it will not be fun.
-Know the local wildlife- Remember, you are intruding into No Petting.
another world when you free dive in the open sea. Some things
Text
bite, some sting, some have poison, and some even want to
eat you, so do not dive without knowing what is in the water.
-Again, DO NOT HYPERVENTILATE during your
breathe up.
-Lastly, there are many rules we could imagine, but the main
rule to follow is: Don’t die.
A common sense approach to dive safety can ensure your
dives are as safe as they are enjoyable, so take care!
