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.

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.

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!!!!!!!