The sporty couple took the children onto the water near the 37-year-old’s Florida home.
Sam and Charlie's mom, Elin Nordegren, was nowhere to be seen but she's reportedly not been thrilled with how much time her ex's new girlfriend has been spending with her kids.
Wearing life jackets the foursome were all smiles and the kids seemed to be at ease with their daddy’s girlfriend.
As RadarOnline.com previously revealed Tiger and Lindsey, 28, met in April 2012 and began dating last November.
On Monday the champion skier tweeted: “Happy Memorial Day. I would like to thank all the men and women who have served and are serving our country. Truly grateful!”