Wait for IP68 Water Resistance
The new and improved OnePlus 7T might ditch the popup front-facing camera for an under-display camera sensor. This means they'll be able to finally offer and certify the phone for proper water resistance. Which, by the way, is one more feature they're going to match the competition on without making the phone cost more money.
So far we've seen several tests that show the current OnePlus 7 Pro is pretty much IP67 water-resistant already, even if the company won't admit it or make the claim themselves. That's mainly to protect themselves from warranty replacements.
However, when they get rid of the pop-up camera later this year we'll actually get a phone from OnePlus that's certified as water-resistant, and that's peace of mind people like paying for.