The poetry device used here is <u><em>metaphor.</em></u>
Metaphor is a poetry device that is used in comparing two unlike things without using words like 'like' or 'as'.
The phrase 'a wave of emotion' is metaphorical because the emotion that is felt at that time is compared to that of a wave without including words such as 'like' or 'as'.
You should do something like monsters at the edge of a lake. THe people in the story go to the lake for vacation but your sister gets sucked by the lake monsters.