Murphy starred again later in the afternoon, following up her previous result with another bullet to go clear at the top of the standings.
'It couldn't really get much better, but there is still a long regatta to go,' she said. 'I am just going to keep doing it one race at a time and see how things work out.
It couldn't really get much better, but there is still a long regatta to go. I am just going to keep doing it one race at a time and see how things work outAnnalise Murphy
'I got a good start to the first race and was leading at the windward mark and led the rest of the way around.
'It was the perfect race and in the second Evi [Van Acker of Belgium] was a good bit ahead of me.'
'I managed to catch up with her, got a few good little shifts on the second upwind and once I got ahead I pulled away quite a lot.
'I couldn't really ask for much more.'
Reigning Star gold medallists Iain Percy and Andrew Simpson shone as they moved joint top of the overall standings.
Percy and Simpson picked up third and second-place finishes to put them at the top of the fleet alongside Norway's Eivind Melleby and Petter Morland Pedersen.
'There is a long way to go but we did a bit better today on the results card,' Simpson said, having picked up an 11th and second yesterday.
In the other highlights, Tom Slingsby of Australia finished the day top of the overall Laser table after coming first and second in the day's two races.
In the 49er class, Australians Nathan Outteridge and Iain Jensen recovered from an eighth-place finish to win the next race.
Allan Norregaard and Peter Lang of Denmark are in the lead, 18 points ahead of British pair Stevie Morrison and Ben Rhodes.
Three-time gold medallist Ben Ainslie could only finish the first Finn race in sixth place as Denmark's Jonas Hogh-Christensen proved he was no one-day wonder.