There are several synonyms for the popular phrase "like shooting fish in a barrel." Some common options include "easy as pie," "a piece of cake," and "a breeze." Another option is "a walk in the park," which suggests that the task is so simple that it's like taking a leisurely stroll. "Child's play" is another variation, implying that the task is so easy that even a child could do it. Other options include "cakewalk," "a slam dunk," and "a no-brainer." Ultimately, all of these phrases convey the same idea - that the task at hand is incredibly simple and requires little effort or skill.