That was interesting! The person that did that is an expert with the liquify tool and I think the video helped me to finally figure out why I've always struggled with the liquify tool - the brush size needs to be rather bigger than I have been using up until now.
The end result looked rather convincing but he left out a small but important detail and as we know, the devil is in the detail! He totally forgot to do anything with her feet, so that by the time he's finished, her feet are no longer in proportion to the rest of her body and look totally out of place!
If you had a laugh at that Photoshop video, you should really take a look at the series of Photoshop tutorials posted here. Well worth taking the time to view!