On a recent trip to Northeastern Thailand I had the chance to visit a place called Chom Dao Beach (หาดชมดาว in Thai). This area is all sandstone which is underwater half the year when the monsoon causes the river to rise. The eddying currents carve the rock into formations and patterns and bore holes that hold water throughout the dry season when the rocks are exposed. Some pools are big enough to never run dry and can support ecosystems of fish which are cut off from the river until the rains return and the river rises high enough for them to rejoin it.
The name of this place means 'star-gazing beach', I believe because it is popular with photographers at night catching the Milky Way reflected in the pools. This place is a bit less popular than a similar nearby attraction where I also shot some photos and I'll have those in a new post tomorrow. In these photos you can see the variety of holes and and patterns which are carved out by the powerful river. I just caught the last of the dry season here, and I actually had to wade across a waist-deep stream of fast-flowing water to access it.