After 2 minutes in under water iPhone X's screen is not working
I did a video with my iPhone X immersing in a lake for less than one minute. It went just 5cm deep in water for less than one minute. Day after, its screen showed dull color. Then iPhone X screen again worked on day two. It's screen went completely dark on day 4. I brought my phone to "Generation Next Communications," one of the authorized dealers for Apple in Sri Lanka, and explained. They said that Apple won't give any claims for issues about immersing in water. They offer me to buy a new iPhone X at 270,000 LKR (806.53 USD).
According to apple's website, iPhone X has IP67 under the IEC standard 60529 certificates. So, it should work in the water. I wonder, without inspecting properly, how "Generation Next Communications" was said they can't repair it or claim? I bought this iPhone X 2019, and the warranty period was over before 6 months.
Please help me to fix this problem.
iPhone X