From 1880 to 1930, mature bald cypress trees (Taxodium distichum) were logged from virgin forests across the American southeast. The harvested trees ranged from 300 to 1000 years old and grew slowly over their lifetime, exhibiting a dense ring pattern that made the wood highly resistant to weather and insects. Logging companies transported the freshly cut logs either by barge or by floating them downriver, with many logs sinking to the bottom to sit undisturbed for a century or longer.
People who accidentally encountered or deliberately recovered these so-called "sinker" logs found a lot to like: beautiful grain patterns, an oil-rich heartwood core that remained virtually pristine, and a variety of tinted colors that were slowly absorbed from the surrounding silt and minerals. Woodworkers and high-end builders coveted these rare remnants of old growth cypress and used the lumber for their most ambitious projects. Despite the great effort and expense involved, crews across Louisiana and elsewhere have sprung up to reclaim these sunken treasures. Some use barges, while others employ SCUBA divers to scour the bottom for sinker logs, which they lift with winch cables. Anyone who engages in sinker log recovery in the US must register for federal and state permits and adhere to strict environmental regulations.
Source: Hurst, Christopher A. (2005). Sinker Cypress: Treasures of a Lost Landscape. Unpublished master's thesis. Louisiana State University, Baton Rouge, LA.