"Scary fish" is a term often used to describe a creature that inspires fear or terror. However, there are many synonyms that can be used to describe these types of aquatic animals. Some may use the term "menacing fish" to evoke a sense of danger or threat, while others might use "terrifying fish" to emphasize the fear factor. For those who prefer a more descriptive word, "monstrous fish" may be a good option. Other possibilities include "frightening fish," "spooky fish," or even "creepy fish." Ultimately, the synonym chosen will depend on the context, tone, and intended effect of the writing.