The Rivered flush hand went like this:

4 limpers
Flop: A57 (one club)

Checks to Marc who bets pot (800)
SB calls.
Rest fold.

Turn: 8c

SB checks.
Marc bets pot again (2400)
SB calls.

River: Qc

SB checks. (pot ~7200)
Marc bets 3K
SB calls.

Marc shows 9846 (one club)
SB shows 2c 3c 4x 6c (giving him the sucker straight on the turn and then the flush on the river)

Given Marc's read on the player, he felt his bet would be called by even a set on the board. Marc has been at the same table with this guy for a while and he has seen some .... "interesting" plays. In fact this is the same player who knocked out Jeff Madsen with a naked flush draw on 678 (two clubs) flop vs. Madsen's T976. The players were all-in on the flop for ~10K each.