The King Kong actress and youngest son Sammy Kai, who has just turned one, spent the afternoon at Balmoral Beach in Sydney, where temperatures hit a balmy 31C.
They played on the sand in the beach in the north of the city and in the sea with other family members.
Day on the beach: Naomi Watts' son Sammy reaches up for a hug as she dries him off after a swim on Balmoral Beach, Sydney today
Wearing a black halterneck swimsuit and a white trilby, Naomi seemed to have a whale of a time in the clear waters, running and diving in.
The 41-year-old, who also has a son Alexander 'Sacha' Pete, two, didn't at all ind getting her hair and face wet.
Naomi is clearly enjoying being back on her home turf for a winter break.
She is British-born but grew up near Balmoral Beach, in the wealthy area of Mosman.
She is now based in Los Angeles with her partner, Wolverine star Liev Schreiber.
Cool down: The King Kong actress takes a dip in the sea in her hometown
Free as a bird: The actress plays in the water
He is in New York for previews of Broadway show A View From The Bridge, in which he's appearing with Scarlett Johansson.
Recently he spoke about having children and how it has affected his and Naomi's careers.
'Kids make a big difference. You want to be there all the time, and when you're both working, it's hard,' he told America's Time Out magazine.
'You've got to negotiate with each other and support each other in that regard.'
