The potholes were created by the grinding action of small stones caught in turbulent water eddies, which slowly bored holes into the riverbed.
The signature turquoise color of the Shima River, often called 'Shima Blue', is caused by the refraction of light through colloidal silica particles in the water.
The bedrock at this location consists primarily of volcanic rock from the surrounding mountain ranges.
The water temperature remains relatively cool throughout the year due to the mountain source.
The Shima Potholes consist of a series of natural basins eroded into the riverbed of the Shima River by swirling sediment over millennia. These geological formations are characterized by their distinct circular shapes and the transparent, turquoise-hued water flowing through them. The site is located in the upstream section of the river, where the geological strata have been softened by volcanic activity. Visitors can view the potholes from a pedestrian bridge and surrounding rocky banks. The depth and clarity of the pools change depending on water volume and seasonal flow conditions.
The view from the Ousenn-bashi Bridge looking directly down into the riverbed.
Wear stable, non-slip footwear as the rocks surrounding the riverbank can be uneven and slippery.
Bring a polarizing filter if using a camera to better capture the depths of the water through the surface reflections.
Visit during a period of low rainfall for maximum water clarity, as heavy rains churn up sediment and obscure the potholes.
Do not attempt to climb or descend steep, unmaintained banks; stick to the designated observation areas and established paths.
Do not enter the water for swimming or wading to ensure the preservation of the geological formations and personal safety.
