A waterspout, or tornado over water, was spotted by members of the public over the Back River near Edgemere on Sunday evening, according to the National Weather Service.
The weather service said the sightings occurred about 6:40 p.m.
About the same time, Doppler Radar indicated a line of thunderstorms moving through the heart of Baltimore's Inner Harbor that are capable of producing strong wind gusts and waterspouts, the weather service said in announcing a special marine warning.
Waterspouts "can develop suddenly and can easily overturn boats and create locally hazardous waves," the weather service said.
The warning is active until 8:15 p.m.