To find out if there are bull sharks in Pohick Bay, I recommend you contact:
* Local wildlife authorities: The Virginia Department of Wildlife Resources or a local conservation organization.
* Local marine biologists or scientists: They may have conducted studies on the area or have knowledge about its aquatic inhabitants.
Remember, while bull sharks are known to tolerate brackish water, they are not typically found in freshwater environments like bays. However, it's always best to be informed and take necessary precautions when swimming in any natural body of water.