I would want to argue that the most obvious physical characteristics relate to the way that the girls who enter the supermarket with their bathing suits on are described. It is clear that this is the central point of interest for Sammy as he works in his monotonous job at the till. Note how he describes the girls and how they enter:
In walks these three girls in nothing but bathing suits... The one that caught my eye first was the one in the plaid green two piece. She was a chunky kid, with a good tan and a sweet broad soft-looking can with those two crescents of white just under it, where the sun never seems to hit, at the top of the backs of her legs.
Note the very physical nature of the description. The girl is "chunky" with a "good tan." Then we are given a surprisingly observant description of her bottom and the way that the two "crescents of white under it" never seem to get tanned. It is clear that Sammy is attracted to the spirit of these girls and their decision to come in to the supermarket dressed in their bathing suits, and we can see this through the physical description that he gives us of them throughout the story.