iPhone not turning on

Hi! Today I found my phone in the sun a little hot and poured some water on it to cool it down. I used it for some minutes and took a small jump in the pool to cool myself down, it was a hot day. I did something else for a minute. When I came back, the phone did not turn on. First I thought the battery has reached zero, and I put the phone in the charger. 4 Hours later, it still didn’t turn on. I tried many different techniques and still black, unresponsive. I tried calling it and there was no sound either. The phone is just turned off and won’t start. My phones battery was weak before and the phone got hot easy before, so that may be the issue. But how can I fix this?

Thanks