Experimenting with purpose-made apparatus  | 
        
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         A current with a steady pattern.  | 
        
         A current that changes periodically.  | 
        
         An irregular current.  | 
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     | Depending on the conditions, irregular currents also occur. | 
Experimental conditions
Water depth : 2.5 cm
Filming conditions
Speeded up 6 times.
240x180:15fps, 320x180:30fps.