Katharine McPhee flaunts her full cleavage while yachting in with ...

She and musician David Foster first sparked relationship rumors about a one-year ago.

And Katharine McPhee made it clear why she won the heart of the Canadian composer, 68, as she paraded her bikini body during a romantic couple's vacation to Capri, this weekend.

While sharing a photo from her trip on Instagram, the American Idol alum, 34, joked about how much effort she put into the social media shot, captioning the picture: 'If only you saw the first 50+ pics it took to get these two.'

Fun in the sun! Katharine McPhee wowed in a black bikini and high-waisted in an Instagram from her Italian vacation with beau David Foster shared on Sunday

Fun in the sun! Katharine McPhee wowed in a black bikini and high-waisted in an Instagram from her Italian vacation with beau David Foster shared on Sunday

Katharine was simple and sexy in a black bikini top paired with high-waisted bottoms in a blue striped pattern.

The singer/actress accessorized with rhinestone framed sunnies as she leaned forward to give up a glimpse of her full cleavage.  

As the caption noted, the photo was taken by her much older love.

The Broadway , who is currently starring in the musical Waitress, gave her 456k followers a closer look at her outfit on her Insta-Story where she showed off a choker and longer charm necklace. 

Redo! the American Idol alum, 34, joked about how much effort she put into the social media shot, captioning the picture: 'If only you saw the first 50+ pics it took to get these two'

Redo! the American Idol alum, 34, joked about how much effort she put into the social media shot,

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