McDonogh sent coach Scott Ward out a winner.
The third-seeded Eagles won the Maryland Interscholastic Athletic Association water polo championship Friday, edging defending champion and top-seeded Calvert Hall, 9-8, in Owings Mills, thanks to a goal by senior Albert Schmickel with 39 seconds remaining.
Ward is leaving his position after 14 seasons and three stints, but he won't officially inform the team of his departure until Monday.
"I never told them," said Ward, whose team upset second-seeded Loyola in the semifinals, 13-6.
"I didn't want it to be about me. That's why. I will still teach and coach swimming here. I had spread myself kind of thin."
McDonogh became the first No. 3 seed to win the title since the league made water polo an official sport in 2000.
Chesapeake-AA 1, Arundel 0: Jake McKenzie scored on an assist from Ryan Keeter four minutes into the second half to lift the host Cougars (8-5-1) over the Wildcats in a 4A East first-round game.
Matt Hudgins had three saves in the win.
Aberdeen 2, Parkville 1, 2OT: Danny Geary and Flakron Salilhu each scored for the host Eagles in Class 3A North.
North Harford 14, Patterson 0: Megan O'Donnell had three goals and an assist to power the Hawks (11-3-1) past the Clippers in Class 3A North.
North Harford will face undefeated Baltimore County champion Eastern Tech on Tuesday.
—From Sun staff reports