The sentence you wrote is mostly clear, but it can be improved to sound better and be grammatically correct. Here's the corrected sentence:
"Remoras travel with sharks by holding onto them with a sticky sucker."
Explanation:
- Use "sharks" (plural) if you mean remoras travel with more than one shark, or "the shark" (singular) if it's just one shark.
- Include the word "by" to show how the remoras travel with the shark.
- "Holding onto them" is good because it means remoras stick to the shark.
So, to keep it simple and clear for a 7-year-old, you can say: "Remoras travel with sharks by holding onto them with a sticky sucker."