Dederer had a solid performance, placing third with a time of 7:51.6.
"Marissa did a really great job with her winter training," said Head Coach Dominic Kahn. "Today's result shows that we are on track for next year."
Meanwhile, Murphy managed a sixth place finish with a time of 6:29.1 in his race.
"Ben's result is a little lower than expected, but he has definitely been the most consistent member of the men's team," explained Kahn. "This shows he is also on track for big things next year."