My Macbook caught water from a glass of water which fell on my desk. Close but not on the computer.
But the new Macbook pro has vent openings quite low and some water must have entered.
It went black and stayed black.
At the Mac-dealer they had a look at it and concluded: SSD burned, main-board damaged and connecting cable ssd-mainboard damaged/corroded. Price-tag close to a new one (1500 euro)
Basically i bought the tools to open the machine (The dissassembly guide at the IFixit site was very helpful) and checked visually. No signs of damage. First disconnected the batteries then i removed the ssd. It indeed was corroded. I cleaned it by carefully removing the corrosion with a very small screwdriver and a toothbrush. Then i inserted and removed the ssd a few times into its socket as to remove some corrosion there.
Also i checked the nearby connectors by loosening them and clean them with the toothbrush.
Then i tested and it worked as new.
Never give up and try to repair using your logical brain.