Well I am from Louisiana and we flooded badly here a few weeks back, not my personal house though. 2 of my customers got flooded and 1 of them pretty badly, 17 of their 18 pc's got wet and both of their servers got water in them.
I got 10 of the pc's up and running with no parts and a hair dryer. I got 1 server up and running with only 1 blown power supply that I had to replace.
Open the side cover and unplug all connectors, if you need to take a picture of where everything plugs in do that first so you put them back correctly. Use the hair dryer to make 100% sure the water is gone inside the connectors and the cable ends. If the cpu got wet take it out and dry the chip and sockets, same with the ram. Take out the bios battery and make sure it is dry and the socket it sits in is dry. If the hard drive got wet and you do not have a backup do not power it on, best to send to a recovery company. If you have a good backup then dry it as best as you can, then give it a try. If your GPU got wet remove it, it could be stopping your motherboard from posting. You can also try drying it with the dryer and try again.
It's definitely not fun working on wet electronics you have to be extremely careful, take your time and don't rush anything. I told my customer I wouldn't even look at the equipment until 2 full days have passed allowing them to dry out.
Good luck with this!