everything on my iPhone works but the screen

bryn, while I agree with my colleague con, I'd suggest to first clean your phone properly. Rice is great for cooking, but it does not repair your phone, nor will it prevent corrosion. Since your phone did have an immersion the first thing I suggest doing is to not longer try to turn it on or charge/sync it. It is easily possible that you are shortening out parts on the logic board i.e. the power management IC, display connector etc. If anything, disassemble your phone using these guides. Once you have that done, clean your phone with high grade isopropyl alcohol and this guide. It was written for a 3g but all the points are valid for your phone as well. Once its clean, replace the battery, this is not optional but a must. If you do not clean your phone properly or change the battery, you will run the risk of failure from corrosion later on. After all that reassemble your phone and re-evaluate for further (if any) damage. Hope this helps, good luck.