Siena (6-8, 3-2 Metro Atlantic) came out on fire, hitting nine of its first 11 shots - including a pair of 3-pointers by Hymes - to lead 21-1 after just over six minutes.
Niagara (3-10, 2-3) didn't lie down, drawing to within four at 56-52 on Karonn Davis' 3-pointer with 9:41 left. Siena used a 6-0 spurt to push the lead back to 10 and though Niagara was able to get it to seven twice, it couldn't get over the hump.
Hymes was 9 of 10 from the floor and Siena shot 52.9 percent. Rob Poole had 17 points and nine rebounds, Lavon Long added 14 and Marquis Wright scored 12 points with eight boards and seven assists.
Niagara was paced by Wesley Myers with 21 points on 6-of-8 shooting, with four 3-pointers in five attempts.