2004 Other Chevrolet Models Repairs after "low flood&qu

Where does one begin on repairs to an otherwise clean vehicle that has been subjected to "low flood" conditions? I believe "low flood" means not above seat level. I have a 2004 Chevy Classic (Malibu?) That I need to get restore to running condition, but don't know where to start on the electrical system to get up to working on the mechanical system. I have nothing in response to a good battery and ignition switch on. I feel sure it is relatively simple electrical, bt need to know where to start. Thank you.