Why is my screen doing this after it got wet

Kiran Diocee sorry to hear about your flooding experience. First off if your laptop "a lot of water landed on top of it" it also got on the inside. What you are seeing are teh results of some water damage. This actually looks like a bad LCD screen but you have to clean your laptop. It will die on you if you do not take care of this.

For now you definitely want to stop using it. Do not charge it or turn it on since that may make a bad situation worse. The very first step I would take is to disassemble your laptop. Use something like this video to help you disassemble your Laptop. Make sure that you disconnect your battery as the very first thing. Remove the motherboard and all parts that are removable. Take a careful and close look at all components and connectors. Truly assess the damage. Look for major corrosion/contamination and evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. You will have to remove all the EMI shields on the motherboard. If you do not remove the shields, you are not cleaning the board. Once you got the gross contamination (muck, organic debris and so on) cleaned, use 90%+ isopropyl alcohol and clean your parts some more. For a proper cleaning, use this guide It was written for an Apple iPhone 3G but it is still pertinent to your laptop and all the boards as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning. Do not use compressed air for the cleaning since that can drive liquid as well as corrosion particles into areas that will cause trouble later on. If you need to use water to clean the debris, use sterile water. Do not use drinking water, . Also, you do not need to leave it to dry for a day. Isopropyl alcohol in the higher concentration will evaporate quickly and dissipate the water. The importance here is the cleaning. It would of course be best to get it professionally cleaned with an ultrasonic cleaner. Do not forget to replace the battery after and replace all thermal paste etc. This is a must and not an option. It will fail if you do not take care of it now. After that, reassemble your laptop and re-evaluate.

If everything is clean and running again, and you still have this bad screen, connect an external monitor and see if that displays the same. If so, it is a component on your motherboard that has failed (video circuitry) If it does not then you know it is your LCD screen that needs to be replaced. You can download the Lenovo Maintenance Guide from here