Photoshop on macOS I need to extend a beach/background image

You might want to make your canvas size to desired size. Then select you beach scene, you can scale the the photo to desired size. If the height is not to be any taller you can scale th photo when hold down the shift key. This will work as long as you do not have to stretch the photo to much that you see it stretched.

otherwise you can try Sameer's suggestion with content aware. Just be careful the clouds look natural.

one other way, you can copy a piece on each side and use gradient to blend into photo.

Hi there,

Thanks for reaching out. This is an interesting question with many correct answers & techniques.

Let me share a few basic ways I could've done it. You can further fine-tune the results.

• You can use Content-Aware crop to extend the landscape.
  

Use a combination of

• Content-Aware scaling (https://helpx.adobe.com/photoshop/using/content-aware-scaling.html)
  Youtube guide for reference - https://www.youtube.com/watch?v=jzVfQJMYJ_w
• Neural Filter - Landscape Mixer - https://www.youtube.com/watch?v=gsE3cLg8imI
• Some patchwork if needed to give finishing touches.

I hope it helps you out, & let me know if it does,

Thanks!
Sameer K