Review of knowledge not written in the scuba diving manual.
What is “Scuba”?
Self-Contained Underwater Breathing Apparatus
Invented in 1943 by the French pioneer Jacques Cousteau san.
He was a leading figure in the history of diving and was involved in the founding of Aqua-Lung and CMAS.
In Japan, Kinzo Ogushi san invented the Ogushi-style diving apparatus in 1918.
What is “PADI”?
Professional Association of Diving Instructors
The world’s largest diving certification organization.
PADI divers outnumber those of all other certification agencies combined.
America, APAC (Japan, China), EMEA
What is “Open Water”?
“Open water” refers to environments where divers can ascend directly to the surface after a dive — such as the ocean or lakes. Conversely, environments like caves or the interiors of wrecks, where the ceiling prevents direct ascent, are called “Closed Environments” or “Overhead Environments.”
In such environments, where immediate ascent is impossible, PADI Open Water Divers are not recommended to dive alone. For safety, divers must dive with advanced divers who have proper training and certification, or take specialized courses such as Cave Diver Specialty or Wreck Diver Specialty.
Basic Restrictions of PADI Courses
Except for a few exceptions, all PADI training courses are designed to teach “self-diving,” which means diving without an instructor or guide. Therefore, in the entry-level “PADI Open Water Diver Course,” students are trained to dive independently up to 18 meters. This is why the Open Water limit is set at 18 meters.
The 18-meter depth limit for Open Water Divers can be extended to 30 meters (with a maximum limit of 40 meters) after learning deep diving methods in the PADI Advanced Open Water Diver Course.
Exception Rules
The diver’s depth limit (the maximum allowable depth) does not apply when accompanied by dive professionals such as instructors or dive guides. Always follow professional instructions.
Physical Fitness Required for Diving
Diving equipment typically weighs around 25–30 kilograms.
To avoid difficulties or giving up during scuba diving license training, proper preparation is essential, including:
1.Being able to swim slowly and continuously for at least 200 meters
2.Staying physically active in daily life through sports, hiking, swimming, or similar activities
3.Maintaining a body condition that is less prone to motion sickness
These preparations are indispensable for safe and enjoyable dive training.
Check Professional Qualifications
When applying for a course or fun dive at a dive center, do you rely only on information from social media or TripAdvisor?
There are two important points when choosing a dive professional or dive center:
・Is the dive center registered with a recognized diving certification organization?
・Does the professional have “Teaching” status?
These two points are crucial.
Dive centers registered with certification organizations are required to have insurance, providing coverage in case of emergencies.
Also, guides or instructors who have not renewed their membership may not have the latest standards and information, which can be risky.
Each certification organization provides a webpage to verify dive professionals. For PADI, you can check the following URL:
https://apps.padi.com/scuba-diving/pro-chek
Tips for Choosing a Dive Center
Social media: ✖
Review websites: △
PADI website: ◎◎◎
Dive centers fall into two main categories:
those operated independently by individuals or companies, and officially registered dive centers that are affiliated with recognized certification agencies such as PADI and covered by appropriate insurance.
PADI-registered dive centers are professionally managed dive shops with comprehensive insurance coverage and full support from PADI.
MSU is a PADI-certified 5 Star Instructor Development Center.
Handling Your Mask
Do not place your mask on your forehead when removing it. If a wave suddenly hits, you could lose your mask.
Never wear your mask sideways or backward like a baseball cap. Heat and moisture from your head can cause fogging, even if you have applied anti-fog treatment.
It is recommended not to remove your mask until you have completely exited the water. This allows you to immediately descend and recover dropped items, such as a camera, during exit.
About Snorkels
In many developing countries, particularly in Southeast Asia where the sea is relatively calm, diving professionals tend to underestimate the importance of snorkels.
However, in places like Hawaii or the Sea of Japan, where large waves are common, not using a snorkel can be life-threatening.
A snorkel is officially designated as essential equipment by PADI, just like a mask or regulator, so especially when self-diving, always wear one.
What Is Nitrogen Washout?
After completing multiple dives in a single day, divers should allow sufficient time for accumulated nitrogen to be eliminated from the body.
For this reason, it is recommended to avoid flying, paragliding, or entering environments where atmospheric pressure drops rapidly for at least 18 hours, and preferably 24 hours or more.
The Relationship Between Depth and Volume
As the table shows, when ascending from 40 meters to 30 meters, the volume increases by 1.25 times. However, when ascending from 10 meters to the surface, the volume doubles. You should understand that ascents from shallow depths require greater caution.
