The Heat actress and The Descendants star were greeted by the sound of cheers and applause from their fans as they disembarked from a water taxi.
Scroll down to watch a video of Sandra and George making their grand entrance.
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Sandra, 49, stole the show in her neon print block patterned bodycon dress. George, meanwhile, looked relaxed and effortlessly cool in a dark suit and striped undone shirt.
The Gravity co-stars happily posed for photos and signed autographs before heading in to a press conference and screening of their film, which will officially open the Venice Film Festival on Thursday.
Sandra and George were spotted arriving yesterday after taking a coach from Lake Como. The Oscar-winning actress travelled with her adorable adopted son Louis, who looked weary after the long journey and didn't accompany his mother to Wednesday's events.
The co-stars have a busy first day at the festival promoting their latest sci-fi thriller, in which Sandra and George play astronauts adrift in space after their shuttle is destroyed.
They will be joined by other celebrities who are gradually arriving to the celebration, including Nicolas Cage, Matt Damon, Zac Efron and Scarlett Johansson.