Samsung Galaxy S6 Edge — Phone fell in water, only switches on when charging.

Hello, my new S6 edge recently fell into water, and I put it in rice overnight to try to make it work again (it wouldn't switch on immediately after the water incident). This morning, I tried again, to no avail, but when I put in the charger, it went to 100% immediately and I could switch it on. Then, I took it out and the phone switched off.
I was already planning on returning the phone because it's less than a month old and already acting up (lags, etc.), but this is pretty frustrating, since I don't know if they'll take it back now.
Anyone had a similar problem and knows how to fix it ?