A multitude of changes, from the larger more obvious ones, to the subtle:
Main edits are replacement of foreground with a sandier beach rather than shells (still with footprints and occasional blemishes, to keep it realistic). Replacement of sky with brighter version (but a cloudy one, so light and shadows on the bach and kids are believable), and the additional of the Christmas decorated cabbage tree.
More subtle retouching is critical to the end result - in this case it's the overall warmer colour tone which helps to tie the retouched elements together and provide an ultimately more summer-like vibe.
