100nl 6max small overpair vs fish

Villain is 50/8 large fishy that is crushing table so far . Has been playing any 2 suited cards and anything that is even decent wit an ace or a face . I thought he had something like a flush draw wit hearts or something like a8 89 910 56 or even something like 79 69 or something like that .

When everything wiffed the river and villain leads pretty big , I thought he could have both of the wiffed flush draws and could be just trying to take the pot down. He has kinda played the passive fish most of the time so im really unhappy when he leads . Do you guys think a passive fishy type is gonna be leading this river wit bluffs enough to call ?

$1 NL (6 max) - Holdem - 5 players
Hand converted by PokerTracker 4

SB: $282.83
BB: $100.00
UTG: $58.78
Hero (CO): $135.94
BTN: $36.70

SB posts SB $0.50, BB posts BB $1.00

Pre Flop: (pot: $1.50) Hero has 9 9

fold, Hero raises to $3.00, fold, SB calls $2.50, fold

Flop: ($7.00, 2 players) 8 7 2
SB checks, Hero bets $4.00, SB calls $4.00

Turn: ($15.00, 2 players) 6
SB checks, Hero bets $10.00, SB calls $10.00

River: ($35.00, 2 players) K
SB bets $21.85, Hero ?