Iphone 3g 16gb water damage help?

I have an iphone 3g 16gb which was in my pocket when I went swimming. I dried the phone using a hair-dryer and put it into rice and it would not work. I replaced the battery and it still wouldn't work, this was a few months ago. I recently decided to just give it a try and plugged it into the computer, it comes on now and displays the apple logo for about 30 seconds then just goes off again. It also goes off as soon as I remove the USB cable and I have tried to restore it in DFU mode at which point it comes on and stays on and is recognised by itunes. It asks me to do a restore which I tried but it got a "error 23" message.