The Seahawks won their second game in the series and improved to 20-15 overall and 12-2 in the CAA. Hofstra slipped to 18-15 and 9-5 in the CAA with its third consecutive loss.
Koenig had reached first on a fielder's choice and stole second. Bass' two-out single off losing pitcher Bryan Verbitsky (0-1) drove home Koenig with the winning run.
Ricky Holden (2-0) picked up the win with two innings of two-hit, shutout relief.
UNCW scored the first run of the game in the third inning on a ground ball out that plated Koenig, who had been hit by a pitch.
Hofstra tied it in the sixth when Jared Hammer's single knocked in Matt Ford, who led off the frame with an infield hit and moved to second on a throwing error on the play. The hit was one of three on the day for Ford.
Both starting pitchers engaged in a pitcher's duel for the first seven innings. Hofstra starter John Tiedemann allowed just one run on four hits over eight innings and struck out eight. UNCW's Mat Batts went seven innings and allowed one run on eight hits with six strikeouts.
Hofstra will look to avoid being swept in Sunday's finale, which starts at 2 p.m.