Great Britain's men's coxless four produced a stunning display to win one of five golds secured by the squad at the Munich World Cup meeting.
With Tom Lucy as an injury replacement for Tom James they were in superb form on the course where they lost their world title eight months ago.
The men's lightweight and openweight double sculls, the women's quadruple scull and men's single also won.
The lightweight men's four and men's eight won silver medals.
"It's been a significantly good day for GB Rowing to open the season's racing programme but we need to keep our feet on the ground," said performance director David Tanner.
"Not every nation took part in some events and there is a long way to go yet this summer."
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Lucy, Andy Hodge, Pete Reed and Steve Williams led from the start and opened up a gap of more than five seconds over the Czech Republic in an event normally won by fractions of a second.
"It couldn't have been better," said Hodge. "That's the best start to the season we've had yet."
But Williams sounded a note of caution adding: "It's only the start. You have to respect crews like the Dutch. They will go away and do their homework and come back stronger and New Zealand, the world champions, weren't even here."
The GB women's quad had a two-second lead by the 500m mark and held a late charge to keep the same margin over Germany at the finish.
"There were a lot of nerves as it was the first race of the season," said Annie Vernon.
"But we went to the start knowing that all our training partners l had already won or taken medals. That gave us such confidence."
Mark Hunter and Zac Purchase were winners in the lightweight men's double and Matt Wells and Stephen Rowbotham took the honours in the openweight category.
Alan Campbell struck gold in the single scull, ahead of some of the world's best in Czech Ondrej Synek and Olaf Tufte of Norway.
However, there was a shock for the reigning world champion men's lightweight four, who were pushed into second place by China.
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