My phone was submerged in water from the bottom

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For now, you must stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse. This may further damage your phone.

The very first step I would take is to disassemble your phone. Since iFixit does not yet have a guide for the main board removal, use something like this guide You will also need to remove the charging board (which is the board with the USB power port etc.) For that use this guide Reemplazo de Conector de Carga Samsung Galaxy A10 Personally I would not clean the charging board but repalce it since that is most likely the boards that got the most water damage. As for the main board, you will have to remove all the EMI shields. If you do not remove the shields, you are not cleaning the board.

Take a close look at all components and connectors. Truly assess the damage. Look for even minor corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. For a proper cleaning, use this guide. It was written for an Apple iPhone 3G but all the steps are 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 since that can drive liquid as well as corrosion particles into areas that will cause trouble later on. You do not need to leave the board to dry for a day etc. 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 ultrasonically cleaned. Replace the charging port and do not forget to replace the battery. It will fail if you do not take care of it now. This is a must and not an option Reemplazo de la batería del Samsung Galaxy A10

After that, reassemble your phone and re-evaluate. For as long as you have not cleaned your board and replaced the battery, everything is just a guess.

Letting the water dry is the wrong thing to do. Water itself is not a conductor and would not harm your electronics but leaving it to dry, deposits minerals and salts that are conductive and corrosive. Those will lead to destructive failure. Always clean water damage!

Repair is War on Entropy!