WJLA reports that four adults and five children were on board two vessels in the Magothy River in Pasadena when the boats collided.
The accident reportedly happened around 7 p.m.
Seven of the nine people were taken to area hospitals. According to the Associated Press, three of the children were taken to Johns Hopkins pediatric trauma center in Baltimore, and one was taken to the emergency room. The children ranged in age from 5 to 12 years old.
AP reports that two adult men, ages 40 and 54, were taken to Maryland Shock Trauma in Baltimore, and a 51-year-old patient was taken to Baltimore Washington Medical Center. Dwyer is 54.
Two people declined treatment. The 5-year-old child was reportedly the most seriously injured. All other injuries were reported to be not life threatening.
A representative for Dwyer confirmed to WJLA that the lawmaker was on board one of the boats.
The accident remains under investigation.