[luckyjimm]

Basically the only hand Ryu beats is the one his opponent has.

sd743 is scared of a check-raise from the flush so doesn't bluff the turn. But on the river, he decides to bluff since Ryu wouldn't have checked the flush on two streets.

Since Ryu raised preflop, his flop bet could have been a continuation bet with a high pair, which unimproved he would fold to a river pot on this scary board.

It is a pretty obvious bluff. I like much more a turn check and river bet when you DO have the nut flush, as your opponent will remember your turn check, think you are weak, and look you up with a set, straight etc.