Sinker logs like the ones above, are pulled from the bottom of lakes and rivers. Sometimes, scuba divers are needed to achieve the extraction.  Most of these logs are hundreds of years old (In one of the pictures above, you can see that the tree was cut with an hatchet). Due to a series of factors (The logs were too big and heavy to be pulled out of the rivers or the logs were caught by currents and were sucked to the bottom)  these logs were trapped by the muddy buttons of these water beds and this created like a time capsule where the wood was preserved in fantastic humidity conditions that made the wood season in a slow natural way during many centuries. Some of the logs are selected for musical instruments construction. The sound that these woods produce is unique and the grain has a beautiful coloration that changes according to the type of mud