2001 Cadillac Deville misfire

Is the check engine light for a misfire. Depending on the severity, water could have ingested into the air pump, or air cleaner box. You almost need to have it scanned, and if at all possible the misfire data explored. If you changed the plugs after the water, then I doubt you have water in the plug ports. If you know what cylinder is misfiring, you can swap the coils and see if the misfire follows. With air injection, this is a bit more involved process, That is where the diagnosis can save some steps. Under extreme conditions where water enters a running engine, it can cause damage, bent rod/valve etc. Due to the water not being able to compress.