The Tigers wished the Tar Heels had never gained their footing.
Junior Ryan Kneipper scored two goals and added an assist as the seventh-seeded Tar Heels defeated Towson 3-0 and advanced to the round of 16 in the NCAA Men's College Cup.
The Tar Heels next face American, which upset Wake Forest 3-0.
North Carolina coach Elmar Bolowich said poor field conditions gave his fundamentally stronger team an advantage.
"In the beginning, you could see both teams were struggling a little bit with the footing," Bolowich said. "And then, obviously, the rationale is, the simpler you play, the better off you are."
UNC opened the scoring in the 23rd minute. Midfielder Grant Porter controlled a failed Towson clearance and chipped the ball back into the penalty box, where Kneipper outjumped the Towson defense and headed the ball past Tiger goalkeeper Chris Hurley into the net.
UNC continued to pressure the Tigers' goal, recording 27 shots. But Hurley, who recorded a season-high 10 saves, kept Towson within striking distance.
"He made some great saves," UNC defender Chris Leitch said. "It's a good thing we had 27 shots against him."
While UNC's offense adjusted to the playing conditions, Towson's offense, which scored four goals Friday against James Madison, never gained any rhythm.