Water damaged iPhone, will not move past the low battery signal.

So I water damaged my phone after using it in a pool and getting it splashed a few times. The screen went off when I was using it while it was still responding to my touch (I could turn the flash on/off). I put it in rice to suck up any moisture. It dried but the water damage indicator turned pink inside the sim tray slot. When I plugged it in to charge the display was back on and it was showing the low battery signal. I put it up to charge and it would show that it was charging. 30 mins later it was still charging (did not boot up and turn on like it normally would.) I unplugged it and tried to boot it but it would not go past the apple logo. The logo appeared, disappeared and this would continue until it would no more do it and when trying to boot it up it would display the low battery signal indicating to charge the phone. Is my battery toast? Is my logic board toast? Is a third-party service better or I should go to apple? Why would a ip68 rated phone get wet?

PS. A year ago I accidentally left my phone in rain for about 15-20 mins but it was okay. How can a a few splashes get my phone wet now? Does a phones water resistance degrade over time (I bought it in November 2018, it got wet yesterday)