An example of simile in popular science writing:
"The unvaccinated population were [sic] like fish in a barrel for the measles virus."
Catherine Carver
Carver, C. (2017). Immune. How your body defends and protects you. Bloomsbury Sigma. (Read about this book: 'Disease and immunity – a biological myth')
This simile relies on a popular idiom: that is, the reference to fish in a barrel is meant to carry an association with the idea that it is easy to kill fish by shooting them when they are collected in a barrel. Anyone familiar with the idiom is likely to make the connection – but the reference is likely to seem obscure to anyone who is not familiar with the saying that 'it is like shooting fish in a barrel'.
Read about examples of science similes