A Coast Guard advisory says a 35-foot to 45-foot whale was reported Monday in the river's Southern Branch near the Jordan Bridge and Paradise Creek. The advisory asks boaters to not feed the whale.
Mark Swingle with the Virginia Aquarium & Marine Science Center says that the whale's species hasn't been identified.
Swingle says the whale has been acting strangely and could be ill or disoriented.
Boaters have reported that the whale appeared to be swimming without a clear direction.
The National Oceanic and Atmospheric Administration says sei whales are usually seen in deeper waters of oceanic areas far from the coastline.