Fourth in our IOSC series is a recap of a presentation by Cmdr. Mark Sawyer, commanding officer of Marine Safety Unit Paducah, Kentucky, titled “T/B APEX 3508 Case Study: Best Practices for Detection and Recovery of Sunken Oil.” APEX 3508 released an estimated 120,500 gallons of slurry oil into the Mississippi River after two tugboats collided near Columbus, Kentucky in September 2015. The majority of the oil sank to the riverbed and Sawyer shared with conference attendees some of the challenges responders faced when recovering sunken oil, lessons learned, and recommendations for future incidents.