iPhone 8 plus water damage

To prevent liquid damage, avoid these:

• Swimming or bathing with your iPhone
• Exposing your iPhone to pressurized water or high velocity water, such as when showering, water skiing, wake boarding, surfing, jet skiing, and so on
• Using your iPhone in a sauna or steam room
• Intentionally submerging your iPhone in water
• Operating your iPhone outside the suggested temperature ranges or in extremely humid conditions
• Dropping your iPhone or subjecting it to other impacts
• Disassembling your iPhone, including removing screws

Minimize exposing your iPhone to soap, detergent, acids or acidic foods, and any liquids—for example, perfume, insect repellent, lotions, sunscreen, oil, adhesive remover, hair dye, and solvents. 

About splash, water, and dust resistance of iPhone 7 and later - Apple Support

Based on what you've said, your iPhone's home button probably needs to be replaced. Replacing the home button is actually a fairly simple repair, but Apple has a policy of not working on water damaged phones. With that being said, I still recommend that you go to the Apple store and tell them that your home button isn't working just to see what they'll say. If they refuse to fix it then you can either attempt to fix it yourself, take it to a repair shop that is not affiliated with Apple, or buy a new phone.

Apple does not cover water damage under any warranty.

Apple will not touch a water damaged phone.

Your options are buy a new phone.

I agree with the last 4 words.