Is the iPhone X waterproof?

No.

The iPhone X does have a degree of water resistance, but is not waterproof.

Apple strongly recommends against submerging the phone for even a moment. Or using it near large amounts of moisture.

Read here:

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

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

Water damage is not covered by warranty.

I’m extremely disappointed about my iphonex.....I paid hkd$4388 for a replacement today just because of me playing golf with my phone in a rainy day yesterday. I thought that my phone should be able to work in such condition so I used my phone as tracker and counter. After ten holes, my phone didn’t function at all. I would rather apple saying that this phone is not water resistant. What a big disappointment!!!!!!!

I’m extremely disappointed about my iphonex.....I paid hkd$4388 for a replacement today just because of me playing golf with my phone in a rainy day yesterday. I thought that my phone should be able to work in such condition so I used my phone as tracker and counter. After ten holes, my phone didn’t function at all. I would rather apple saying that this phone is not water resistant. What a big disappointment!!!!!!!

iPhone X is water resistant. It is NOT waterproof. Do NOT submerge your iPhone X. And if you do, water damage is NOT covered under iPhone warranty.