Diving2

　Yesterday's first diving we had very interesting experience. We see something as Black in 25 meters depth under the sea, although we see it as Red above the sea. But about something blue and fluorescent color above the sea is still same color int the sea. I did not know why only red one change its color, in other words, only light ray of red was shut off in the sea. Anyway, it was very interesting.
　Yesterday's second diving was "Peak Performance Buoyancy". It was very difficult for me. If the power of buoyancy is stronger than the power of gravity (this situation is called "Plus Buoyancy"), our body moved up in the sea. As our body moved up, the presser of the water decreases and the volume of the air in our diving devise (like floating tube) increases. So, the power of the buoyancy increase too because the buoyancy is proportional to the volume of air.
　Then, if we leave a plus buoyancy, we rise up at an accelerated pace. It is seriously bad for our health. So, we should get rid of air when we have a plus buoyancy. And we should reach the point where the power of the buoyancy and gravity are same (this situation is called "Neutral Buoyancy"). The purpose of this training was to learn keeping neutral buoyancy. But I am not good at it now.
　Yesterday's last diving was "Under Water Navigation". In this training, we learned how to use compass in the sea.
　And we will dive next week as "Drift Diving" and "Aware fish".