Stop trying to start it. Remove the power cable completely then totally immerse the tablet in uncooked rice and leave it there for at least 24 hours. With luck the grains will absorb the liquid and if it's not too late, rescue the machine from disaster.
Droping anything on water such as tablet or mobile. In case don't turn on your device, Keep you table in Sunlight whole day and in night you need to provide heat. Don't burn it remember it. For further Contact repairing shop. Thank you.