Rivers finished with 20 points and Kenneth Ortiz had 19 points and a career-high 11 assists for the Seahawks (9-5, 3-0 Northeast Conference), who had lost three straight to the Blackbirds. Mario Moody also tallied 19 points, a career-high.
LIU (5-10, 0-3) led 27-23 before Moody hit a layup that sparked a 19-4 run for Wagner over the final 6 minutes of the first half. The Seahawks took a 42-31 lead into the break, and after LIU cut the deficit to 47-43, used a 13-2 run to take the lead for good, 60-45.
Wagner outrebounded LIU 37-24, shot a season-best 59 percent (29 of 49) and hit 9 of 10 from deep.
Jamal Olasewere's 16 points led LIU.
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.