Crunch time for Aussie rowers

It's Rio or bust for four Australian crews in the World Cup rowing regatta starting this weekend in Switzerland.

Four crews will compete in Lucerne in the "Regatta of Death" - a final chance to qualify for the Rio Olympics.

The men's and women's eight, lightweight women's double sculls and Rhys Grant in the men's single sculls are competing.

The eights and women's double must finish top two in their finals to qualify their boats, while Grant has to place in the top three.

Grant has the biggest field, up against rowers from 17 other countries, with the final to be raced on Sunday.

The women's double of Hannah Every-Hall and Georgia Nesbitt will compete against crews from Greece, Italy, Netherlands, Romania, Switzerland and Sweden, with heats on Sunday and the final on Tuesday.

The Australian men face a tough challenge to get over the top of crews from Spain, Italy, Poland and the USA while the women have four other contenders in the eight's race.

Their heats are also on Sunday with the finals on Tuesday local time.

Rowing Australia's general manager of sport Jaime Fernandez said the crews were well-prepared.

"There is a good mixture of youth and experience amongst our crews and were hopeful that this translates into some strong performances on the water," Fernandez said.

"There has been an excellent level of collegiality, common purpose and collaboration against athletes, coaches and staff alike."