Some sharks can stay motionless on the sand (white tips reef sharks, nurse sharks, etc.).
These sharks don't have to swim to bring oxygen to their gills like other sharks (grey, hammerheads tc.)
Parrotfish create a protective envelope around them when they are sleeping.
So, don't put the light on them during night dive to don't to wake them up and break this envelope.
The kakihona sushi (sushi wrapped in persimmon leaves) are really the best!
To eat them, you have to go to Nara!
