I think Kim outweighs Scarlett by around 20 lbs., it's not the only thing, but on beach sand having that big a weight edge HAS to be an advantage. (Stamina is also a factor to consider, and there I give Johansson the edge.) But as usual in a fight, it will come down to mental toughness....
...and the writer's ability to deftly weave a coherent narrative using simile, metaphor, and classical allusion.
I hope to see the winner (and the writer) happily gamboling off the beach sand - hand in hand - toward the library to check out the reference room copy of Roget's Thesaurus to find out what the hell I was talking about! (I know I AM!)
BTW: Have I mentioned HOW MUCH I LOVE these Beach Tour stories? If not, I really, really, do!! (so know that stuff above was posted with love and affection to any and all writers to give us the stories! It's appreciated more than you know.)