Glover and Swann have proved hard to beat this season but were challenged all the way - though British coach Robin Williams had no complaints.
"They probably would have liked to have been further in front but they got the job done", he said.
"There are some quick pairs around and it's good to be tested".
Eight British crews progressed into the semi-finals with Frances Houghton and Victoria Meyer-Lake advancing straight to Sunday's women's double sculls final.
Great Britain's newly-tweaked and Olympic medallist stacked men's eight - record breaking winners at last week's Henley Royal Regatta - finished second behind a powerful USA crew.
Alex Gregory, who missed the World Cup at Eton Dorney with a virus, is back in the boat along with Andy Triggs Hodge, Pete Reed, Tom Ransley, Dan Ritchie, Will Satch, Mo Sbihi, George Nash and cox Phelan Hill.
"Lucerne will be our toughest test in this post-Olympic season, with a strong entry and World Championship selection at stake," said GB Rowing Team performance director Sir David Tanner.
"It's a great chance for our rowers to step up again after a solid season so far."
- Sports & Recreation
- Frances Houghton