Flopped nut straight, 3 flush comes in on turn

[CubicZirconia]

UTG is 76/9/.47 after 90 hands. Horrible player. SB is 37/12/1.75 after 60 hands. Doesn't like to fold his blinds to raises. I felt like I should have bet the turn here, but when he called my flop raise I was putting him squarely on a flush draw. Do I call the river bet? Any input is appreciated.

Poker Stars - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 6 Players - (LegoPoker HH Converter)

SB: $21.50
<font color="black">Hero (BB): $35.40</font>
UTG: $38.70
MP: $24.65
CO: $28.25
BTN: $14.65

<font color="black">Preflop:</font> Hero is dealt 7[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/spade.gif[/img] (6 Players)
<font color="red">UTG raises to $0.50</font>, MP calls $0.50, 2 folds, SB calls $0.40, Hero calls $0.25

<font color="black">Flop:</font> ($2) 6[img]/images/graemlins/diamond.gif[/img] 9[img]/images/graemlins/diamond.gif[/img] 5[img]/images/graemlins/heart.gif[/img] (4 Players)
<font color="red">SB bets $0.50</font>, <font color="red">Hero raises to $3.75</font>, 2 folds, SB calls $3.25

<font color="black">Turn:</font> ($9.50) Q[img]/images/graemlins/diamond.gif[/img] (2 Players)
SB checks, Hero checks

<font color="black">River:</font> ($9.50) T[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">SB bets $5</font>, Hero...

[catfish_01]

I would call this river bet since you checked the flush card turn; I think it's correct to keep the pot small, though.

I may be a bit off base here; but you need to be good about 25% of the time. It does look like the river bet is a value bet, but, SB could be doing this with a hand like a set or two pair (maybe QT), or air, enough for you to be ahead.