■Feeling of distance in the water

Underwater, fish appear larger (4/3 times) than they are, or closer (3/4 times) than they are.


This is due to light refraction as light enters the mask (in the air) from water.


As a result, when reaching out for something like a rope which will appear larger and closer than it really is, you should be careful not to misjudge distances.

■Underwater creature

Some organisms have poison, others attack when stimulated.


Many creatures camouflage and hide on stones and sand on the sea floor.


Care must be taken not to touch the underwater creatures and the sea floor or to stimulate the underwater creatures.

Watch out for the sea floor

■Buddy system

The dolphin swim diving must be done by two or three people in one set and not by one person. This is called a buddy system.


Buddies act together and always make sure each other is safe.

Act together

■Poor physical condition during the course

If you feel unusual during your participation in the program, immediately signal the instructor and stop participating in the program.