St. Joseph went 20-1-2 and won the first South Jersey Non-Public title. The Wildcats' lone loss was to state power Oak Knoll in the Non-Public championship game.
DeMarco has been St. Joseph's head coach for 18 seasons. He was an assistant for 12 years before that.
He is 268-60-29, with 13 Cape-Atlantic League division titles and five South Jersey championships.
But DeMarco said he never experienced a season quite like this one. And this season was encapsulated by the play made by his daughter Emily, with a little more than a minute to play in the South Non-Public title game against Bishop Eustace.
Eustace entered the game as the heavy favorite, as the Crusaders were the No. 2 team in the Newark Star-Ledger's state rankings.
St. Joseph was on a roll. The Wildcats had beaten Olympic Conference power Camden Catholic in the semifinals.
"Our whole goal was to pull Camden Catholic and Bishop Eustace off the turf," said John DeMarco, noting that the Irish and Crusaders were speedy, skilled teams that flourished on their home, artificial-turf fields.
On St. Joseph's well-worn grass field, the Wildcats slowed the game and beat Camden Catholic despite a disadvantage in possession and corners.
The same thing happened against Eustace. But the game seemed headed for overtime with the score tied at 1-1 when Emily DeMarco, a senior midfielder, corralled an insert off one of the Wildcats' rare corners, maneuvered past two defenders, and used a reverse chip to score perhaps the biggest goal in the history of the program.
"The first thing I did was look at my dad," Emily DeMarco said.
John DeMarco coached his daughter Megan, a senior during the 2010 season, and Emily in their four-year careers.
"When it's one of your own, they know how dedicated you are to the program," John DeMarco said. "It's like they are looking out for you.
"When Emily scored that goal, she looked right at me, and that's something that I'll never forget as long as I live."
Like her older sister before her and her seven senior classmates this season, Emily DeMarco will leave the program. But her dad isn't going anywhere.
His third daughter, Riley, is a third grader. The coach said she's more advanced than her sisters at her age.
"Nine more years," John DeMarco said, counting the days until Riley's senior season.