The Tigers entered the second half trailing 5-4 but scored five unanswered goals in the third quarter.
DeNapoli got his 11th career hat trick during the offensive flurry, recording two of his four goals back to back in the seventh and eighth minutes.
Seider, playing in his first college game, also scored back-to-back goals in the period and added a third in the fourth quarter.
Towson outshot the Panthers (0-2) by 41-26 and collected 25 ground balls to High Point's 14.
Navy 18, VMI 5: The Midshipmen surged past the Keydets at home, winning the teams' seventh consecutive season-opening matchup.
Senior attackman Sam Jones (Severna Park) paced Navy with four goals and six assists, while the team's defense allowed the fewest goals since an 8-2 upset of then-No. 6 Johns Hopkins in April 2012.
Eleven Midshipmen scored, with attackman Tucker Hull providing three goals and two assists and midfielders Pat Durkin and Austin Heneveld adding two goals apiece.
No. 1 Duke 16, Jacksonville 10: The visiting Dolphins (0-1) opened a 3-0 lead, but the Blue Devils (1-0) responded with seven unanswered goals to take control.
Attackman Josh Dionne scored five goals, tying a career high, and four Duke players scored two goals apiece.
Midfielder Dakota Rohlin scored a hat trick for Jacksonville.
No. 4 Denver 14, Air Force 8: The visiting Pioneers overcame a 3-1 deficit to rout the Falcons in the season opener for both teams.
Attackmen Wesley Berg and Jack Bobzien turned in dominating performances for Denver with five and four goals, respectively, and midfielder Jeremy Noble added four assists. Attackman Tommy McKee had a hat trick for Air Force.
No. 10 Virginia 13, Richmond 12: The Cavaliers held on down the stretch of a back-and-forth game to beat the host Spiders.
Richmond, playing in the program's first Division I game after moving up from the club level, scored seven straight goals in the first half and took a one-goal lead into the break.
Cavaliers attackman James Pannell's three second-half goals helped spark the comeback win for Virginia (2-0).
Navy 14, Longwood 8: Five Mids scored at least two goals to power Navy past the host Lancers in the season opener for both teams.
Mids attacker Loren Generi had a game-high four goals, and midfielder Casey Browne added a hat trick.
Navy trailed Longwood late into the first half but scored eight straight goals to secure the win.
No. 1 North Carolina 20, No. 4 Florida 8: Sydney Holman and Abbey Friend scored five goals each to lead the Tar Heels (1-0) past the visiting Gators (0-1).
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North Carolina outmatched Florida's defense, taking 41 shots to the Gators' 24 and putting the game out of reach with nine goals in the first 20 minutes of the second half.