Chosen Solution
So my iPhone 8 has a big crack at the bottom of the phone on the back, I was just wondering if it was still waterproof. Thanks for the help!
The iPhone 8 is not waterproof, it is water resistant. Splash, Water, and Dust Resistant3 Rated IP67 under IEC standard 60529 If the back is cracked, I would consider the water resistance to be even less effective so you should be extra careful around water.
On my iPhone XS, I cracked the front screen and when I went to apple they said not to take it into the water unless it was fixed. I decided to replace the front glass with apple and now it is water resistant again. :)