I went with my iPhone 11 Pro under the water

I went with my Iphone 11 Pro under the water (depth was 50cm) and when I went out of water it worked for about 15 minutes just right, then it showed up a green line from bottom to top of the screen, minute after that showed another one and another one (about 6 green lines)... and than phone turned off for about an hour. I had 40% battery before it died, but I put it on charge for about 10 minutes, than it turned on. After that green lines are constantly showing and phone js turning off and on, it doesn’t work more than 10 minutes. I don’t know what to do, it should be waterproof and it wasn’t under the water for more than 5 minutes . I just took a few photos under the water and that happened. Please help me.

[Re-Titled by Moderator]