Penalties have again proved costly for Jessica Fox with the Olympic slalom canoe champion forced to settle for a second silver medal at the World Cup in Prague.

On day one Fox was quickest in the kayak event but was relegated to second place due to two gate touches, which added four seconds to her time.

The triple Olympic medallist suffered a similar fate in the C1, posting a time of 93.94 but had four seconds added to finish 1.59 seconds behind home town hero Gabriela Satkova.

Germany's Andrea Herzog, who won bronze in the event at the Tokyo Olympics, placed third.

With less than 50 days to go until the Paris Games, Fox said she was pleased with her speed but frustrated by the uncharacteristic gate penalties.

"It was a really good run, there were some good attacking bits, I improved on my semi but unfortunately the penalties cost me the win today," the 29-year-old said.

"I was a bit frustrated with the last touch but very happy to be racing here.

"It's an amazing atmosphere [here] and good to be on the start line feeling those nerves."

Fox will compete in another World Cup Krakow in Poland next weekend before heading to Paris for a solid block of training.

"This is our racing block and then we'll get back to some good training with less than 50 days to go, it's exciting," Fox said.

Fellow Australian Kaylen Bassett made it through to the top ten final where he delivered a personal best to finish seventh overall.

Olympic K1 champion Jiri Prskavec ensured a Czech double, winning the men's C1 event.

The kayak cross competition on Sunday doubles as the final Olympic qualifier, with Fox's younger sister Noemie looking to book a berth to Paris.

Noemie was the fifth fastest in the time trials on Saturday.

AAP