Hello rebeccarouse,
If you need to backup your iPhone but are not able to see the iPhone's screen because of water damage, there are a few things you can try.
- Backup your iPhone using iTunes
- Transfer your purchases from the iPhone to iTunes
- Import your pictures to iPhoto or Aperture as a secondary backup of the pictures taken with your iPhone.
The links below will provide more detailed instructions.
How to back up your devices using iCloud or iTunes - Apple Support
https://support.apple.com/en-us/HT203977
Open iTunes and connect your device to your computer.
Save content that you downloaded from the iTunes Store or App Store by clicking File > Devices > Transfer Purchases.
Click File > Devices > Back up.
After the process ends, you can see if your backup finished successfully by clicking iTunes Preferences > Devices. You should see the name of your device with the date and time that iTunes created the backup.
Import photos and videos from your iPhone, iPad, or iPod touch to your Mac or Windows PC - Apple Support
https://support.apple.com/en-us/HT201302
I hope this information helps ....
- Judy