OP, when you say “dive”, are you referring to using a diving board or snorkel / scuba? Not that it matters, but there is a big difference.
IP68 provides protection for up to 1.5 m depth for up to 30 minutes. When you use a diving board, normally you will descend further than 1.5 m into the water and there may be a pressure shock that’s effectively the same as greater depth. When snorkeling, it’s easy to descend more than 1.5 m. Obviously scuba involves much greater depths.
The point of IP68 is not to facilitate using devices underwater, but rather to protect them against accidental exposure to water, such as heavy rain or wearing them into a shower or putting them into the washing machine. An HA would not work properly underwater. They are designed to work in the air not under water. Even with poor hearing, you can hear much better underwater, anyway.