My REDMI NOTE 11 stuck on a boot loop. How to get it out of it?

Hi mate, try to press and hold volume up and power button untill it gets you to boot menu. When you get there try your volume up and volume down button and check that they are working properly. A common issue is that volume down button is stuck and is permanently on and when you try to boot the phone it does permanently force restart. If everything is ok with your buttons, try to select wipe cache and then reboot the device. If problem remains, then if you don't care enough of your data you could try factory reset from the same menu as i mentioned before. Note that the device will boot as new but it will be locked with your gmail account.

@simas17599 your worries should not be about the boot loop but on how to get your phone cleaned after the water immersion. You said you dropped it "into the sea", which makes me think that you immersed in into salt water.

First and foremost, stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse.

Salt Water is corrosive and will get your components to corrode very severely. The very first step I would take is to disassemble your phone. Use this guide for the charging board and this one for the main board. Once you have to boards removed, take a careful and close look at all components and connectors. Truly assess the damage. Look for major corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. This "lime on screens wire also lime on where the wire goes" is a telltale sign of corrosion and salt water damage.

I suggest that you clean your boards and all ribbon cables a couple of times with sterile water, not drinking water (that might have helped right after it got submerged in the salt water). Use a soft brush and clean it very, very thoroughly with the sterile water. With the amount of corrosion that I envision, you will have to remove all the EMI shields of your main board. Once you got all of the gross contamination cleaned, use 90%+(as high as you can get) 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 phone 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. That can drive liquid as well as corrosion particles into areas that will cause trouble later on. Do not use drinking water, if you need to use water, use sterile 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. If you can get it professionally cleaned, than do so. This is not an easy task and you may need to consider professional help for an ultrasonic cleaning. After you cleaned it, replace the battery. This is a must and not an option. It will fail if you do not take care of it now. Then reassemble your Xiaomi and re-evaluate. Until it is cleaned, everything will only be a guess. It is very possible that you have a bad LCD and replacing the display assembly will most likely be a must do. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try.