Realism can be used to enhance a reader’s experience with a story by making the fictional world feel less fictional. For example, a character who has been deprived of water for several days could start to suffer from dehydration – a deceptively dangerous condition. Rather than continuing to perform physical tasks at an optimal level as if water isn’t something humans need, the character will grow weaker and slower as their body comes closer to expiration. This realistic portrayal of such a scenario can help a reader become more immersed in the character’s situation.
Unfortunately, realism may also have the opposite effect by conflicting with a reader’s expectations. For example, when the hero puts a suppressor on their rifle, the reader will probably expect the firearm to make a barely audible “poof” when fired. Realistically, this would probably not be the case. The suppressor would offer more space for the gases to cool and expand before hitting the open air, but unless the hero is using some sort of subsonic ammunition, the bullet will still break the sound barrier, thus still resulting in a quite audible little “boom.” But this isn’t what many readers would expect, so realism is often sacrificed in such a scenario by many writers.
And at times, writers may even neglect realism in favor of progressing their story in a certain image, however unrealistic it may be. Another fine example is when swords enter the story. A writer may display a grandiose scene where the hero and the villain dance around with swords for several minutes, all the while having a conversation. A real sword fight likely wouldn’t last more than a few seconds. The characters would draw their swords, pumped up on adrenaline, and then someone would get cut to ribbons in an instant. And thus, a realistic portrayal of a sword fight may often be so anticlimactic it never even occurs to a writer’s mind (or a reader’s) that their epic scene is in fact, quite outlandish.
So then, what to do about the problem of realism. That depends on the story you’re trying to tell. If it’s meant to be far-fetched, then you might want to avoid realism to give the reader a sense of outrageousness. On the other hand, is this tale meant to be taken seriously? If so, you should consider researching anything and everything you put into your story that you’re unfamiliar with.
Does your protagonist wield a firearm? Do your homework. Decide what type of weapon they have, and what ammunition they load it with. One “pistol” could act completely different from another, and two different cartridges could produce wildly different results, even when fired from the same weapon. Did the hero incapacitate the villain by shooting him once in the arm? If so, the hero must’ve been dreaming, because that’s not how it works in the waking world. Research ballistics and the effects of gunshot wounds on the human body, as well as the probability of accurately targeting someone’s arm.
Find a way to balance the realism in your story. Consider the tone and purpose, the message you’re trying to convey. A safe way to determine the amount of realism your story needs may be to measure how seriously it’s meant to be taken. The more serious the story is, the more realistic it should be, and vice-versa. But this is entirely up to you.
At the end of the day, what’s most important is to do your research. No matter how realistic – or unrealistic – you want something to be, you can’t accurately portray what you don’t understand. So, before your character puts on those boxing gloves or picks up that sword, be sure you read up on the material yourself. Make sure you know what your hero is getting into.