Britain's Bill Lucas and Sam Townsend finished fifth in the men's double sculls final as New Zealand's Nathan Cohen and Joseph Sullivan took gold.
The British pair clocked a time of six minutes 40.54 seconds with Italy taking the silver and Slovenia the bronze.
Britain's men four and men's lightweight double boats are both through to their finals at Eton Dorney after winning their semi-finals.
All 13 boats that Britain entered have qualified for the Olympic medal races.
GB rowing glory
- Women's pair
- gold medal
- Men's eight
- Lightweight men's four
- Men's single sculls final
- Alan Campbell
- Men's quadruple sculls final
- Stephen Rowbotham, Charles Cousins, Tom Solesbury, Matthew Wells
- Men's pair final
- George Nash and William Satch
- Women's double sculls final
- Anna Watkins and Katherine Grainger
Lucas and Townsend, who are in the first season in the double scull after switching from the quad, finished a strong fourth in the last World Cup before the Olympics.
However, they could only manage the third fastest time in the semi-finals to scrape into the final where they were isolated out in lane one.
The British duo took it out hard to lead after the first 500m, but Italy, New Zealand and Slovenia pushed through at the half-way point and they could not respond despite huge support from the crowd.
Mind games were at play in the men's four semi-finals as Britain and Australia - the two crews favoured for gold - faced each other for the first time in this regatta.
Australia have won their last two battles, beating the British crew in the semi-finals and final in the last World Cup.
The Australians went out the harder of the two crews, leading until 500m to go, at which point they appeared to ease their stroke rate as the British crew upped theirs.
The British quartet of Alex Gregory, Pete Reed, Tom James and Andrew Triggs Hodge rowed through to take victory by half a length to the delight of a capacity crowd.
The two crews will be joined in the final by the Netherlands, the United States, Greece and Germany.
Defending Olympic champions Zac Purchase and Mark Hunter in the men's lightweight double have had an indifferent season, winning the first World Cup regatta before trailing home sixth in the next two.
However, the duo say they have moved on following a six-week training camp ahead of this regatta and demonstrated that with a good win over New Zealand in the heats.
France, who won gold in the second World Cup of the season, pushed them close in the semi-final but the British pair held on in the final 500m to win by half a length and retain hopes of defending their title.