Is my iPhone safe to use after accidentally dropping it in water?

Review the information here about what to do when your phone gets wet, and pay particular attention to wait on charging.

About splash, water, and dust resistance of iPhone 7 and later - Apple Support

Phones have a Liquid Contact Indicator (LCI), and you can view the status here:

Water and other liquid damage to iPhone or iPod isn't covered by warranty - Apple Support

Power off your iPhone and leave it upright with the port facing down so it can dry out, and give that about 24-48 hours. Hopefully it still works, otherwise If it won’t turn on, the water damage has caused corrosion to all the parts and has stopped functioning. Water damage cannot be repaired and Apple won't even service your iPhone if it has been exposed to water damage, so would most likely look at a replacement.

Power off the phone if it is on and let it dry for at least 24 hours. Do NOT put the phone in rice.

Stand the phone on end and lean it against a wall so the ports are at the bottom of the phone to allow any water to drain out.

Cross your fingers and try to power up the phone.