Shanghai - Ferrari's Sebastian Vettel splashed his way to the fastest lap Saturday in a wet final free practice for the Chinese Grand Prix as Mercedes chose not to set a time.
World champion Lewis Hamilton and Nico Rosberg sat pensively in the Mercedes garage after briefly taking the plunge in hazardous conditions, while Vettel clocked a time of one minute, 57.351 seconds.
Ferrari team-mate Kimi Raikkonen ran 12th fastest in 2:00.812 before returning to the pits and slipping into a raincoat after a session delayed by 15 minutes due to a morning downpour in Shanghai.
Drivers and mechanics stared glumly at puddles in the pit lane before Valtteri Bottas tiptoed out in his Williams, the Finn eventually producing the second-quickest lap, 0.7 seconds behind Vettel on intermediate tyres.
With visibility poor and cars aquaplaning, Mercedes decided not to risk a flying lap.
Mexican Sergio Perez steered his Force India around in the third fastest time of 1:58.689 with the Toro Rosso of Carlos Sainz fourth and Esteban Gutierrez fifth quickest for newcomers Haas.
Hamilton, who has won a record four times in China including the past two years, will begin Sunday's race with a five-place grid penalty for a gearbox change. He did just a single installation lap on Saturday ahead of qualifying later in the afternoon.
Rosberg is chasing a third successive victory after winning the season's first two races, but Ferrari, who struggled with reliability in Australia and Bahrain, have shown genuine pace during practice on the first two days.
Four-time world champion Vettel placed third in last month's Australian Grand Prix where Raikkonen's engine caught fire, but in Bahrain it was Vettel's turn as his engine blew on the out lap as Raikkonen finished runner-up.
Spain's Fernando Alonso, cleared to return for McLaren in China after fracturing ribs in a terrifying crash in the season-opening race, also opted not to attempt a flying lap.
Ferrari are the most successful team in China with four victories -- including the last of Michael Schumacher's record 91 race wins 10 years ago.