Greetings!
We appreciate your post in the Apple Support Community. Given the situation, the best course of action is to immediately take your iPhone to a certified repair center or directly to Apple. Even though the iPhone 16 Pro Max is water-resistant, this resistance can degrade over time or due to wear, and water exposure can still cause serious internal damage. Since the phone is already showing issues, such as turning on and off, it is crucial not to try to dry it yourself or continue using it, as this might lead to further damage, including short circuits or corrosion.
> Offizieller Apple Support
> Apple Store - Store finden - Apple (DE)
For English speakers, we have a dedicated community here: discussions.apple.com. Since your message is in English, we warmly invite you to join us there.
Thank you!