A metaphor compares things WITHOUT using like or as. similes use like or as. the first one, with "stomach swims", seems like personification,giving an object human qualities. I would go with the second one, some assume a simile to branch underneath metaphor, I'd assume. the first one isn't comparing anything, so it's probably the second choice.
"You should volunteer to tutor! Imagine all of the students you could help with tutoring. I would want somebody who knows the subject to help me if I was struggling."
Explanation:
With pathos, you want to appeal to someone's emotions. You want the person to feel some sort of emotion.
