Water damage is definitely an indication that something will be an issue.
The fact that you get 1.5v then quickly drops to 0v would almost indicate a very likely short to ground.
What is your resistance to ground? I would bet it is very low.
If you get 0v to the battery, then the charge IC isn’t passing voltage so that could potentially be victim number one. Here’s how we can test this.
Do you get any voltage going to the charge IC?
If so > replace charge IC (BQ24193 see here for location: [INFO] Board diagram and part numbers) - however I would recommend to only do this if you have a microscope as it is very easy to knock the components close to it off the board.
If not > then something else is the issue, you’ll need to go around and check where power is going to and where it is not.
In any case, I would strongly recommend removing the board from the console so you can also see the underside, especially with a water damaged device, we need to get the full picture. If you could upload some pictures that may be helpful - we might see something you don’t (a second pair of eyes is always handy)