Answer to: Dropped Phone in Waterfatal error in not turning it off instantly. but the SE does have a bit of waterproofing; its not waterproof but it does have better waterproofing than the previous models (similar to the 6 and 6s in fact) in this case the immersion (if your story is to be believed) was minimal; but the time taken to remove power, and therefore short circuits, wasnt. Thats where the damage will occur. youre just going to have to wait and see and if you do get it back up and working and your photos recovered i suggest you open a Google account and store all your photos online with google for free!
Answer to: Why is my screen black?couple of things; did you not disconnect the battery when you did the swap? and secondly have you disconnected the battery since? some screen swaps need a full power down and on again to activate the screen correctly. could also be a duff new screen, or missaligned connections thats going to be a lucky solution for you if thats the case....golden rule: always disconnect the battery! if not then the other answers are your most likely scenario
Answer to: replacing board to home button flex cable on back plate.fingerprint and home button are all one unit. the ribbon cable that runs up the back of the shielding is just a ribbon cable. as long as you dont change the home button then everything should work just fine.