iPhone 13 Pro Max slipped into water for seconds. What do I need to do?

Neither. Rice does not work and you can only risk getting pieces into the charging port. A fan can just force any water further inside the device where it can really do more harm.

Turn it off, set it aside with the charging point pointed down and leave it for 24 hours. Then try turning it on and see if it works and if it will charge. If not, understand that water and electronics do not mix, make a Genius Bar appointment at the nearest Apple Store to have the device examined by Apple. They will explain your options, but it could be a very good chance you will need to replace it.

Make a backup ASAP, you never know if or when it will die.

“iPhone 13 Pro Max slipped into water for seconds. What do I need to do?: Dry it in rice? In front of a fan?”

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Troubleshooting Water-Inundated iPhone:

There might be an option, after a few days…

Extracting the Water:

Take this to a local retailer. Many retailers have devices designed to extract water from a mobile phone. Local one in my rural area do, and I've used one myself

Just for the record, the iPhone 13 Pro Max is rated IP68 for water resistance, meaning it can withstand a maximum depth of 6 meters for up to 30 minutes under controlled laboratory conditions. However, this is not a permanent condition, and Apple Support advises against intentional submersion, swimming, showering, or exposure to high-velocity water. 

iPhone 13 Pro Max - Technical Specifications - Apple Support

I think a dip for a few seconds and you should be fine. It’s been a day or so, visually examine your iPhone for and unusual changes. If it looks and feels normal, power it up.

“To TheLittles, Oops, I meant to say “first time user of this community, thank you”, (to those who responded). I guess Siri missed took time for “I’m”. I’m old.. I make a 2 letter error.”

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No worries. I’m not too fond of nor reliable on text-to-speech, myself, when responding to others on forums or messages —because the wrong this can come out, and be mistaken. This might come down to troubleshooting Siri, as its own thing to troubleshoot. Start here: If "Hey Siri" isn't Working on your iPhone or iPad - Apple Support

“First, I’m using this community thank you”

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🤔You think so? These forums are about feedback and troubleshooting. —such as spreading ideas of fixing your issue.