you can try,
I once returned a 21 inch crt...it's garbage now, but in those days you could buy those for 600 euro.
I wiped it clean as good as I could and they gave me a brand new one.
Just make sure you don't tell them it was water damage.
Once Dell technicians open the laptop it will be pretty obvious they will notice water damage. Saying this since I have seen many water damaged laptop.
Ask Dell customer service if you are qualified to buy their extended warranty.