I had to drive through some pretty high flood waters last thursday, like up to the bottom of the hood at times. Car ran fine until tuesday. Then, without warning it just died mid-drive. Now I'm getting no spark from the coil. Would the opti have anything to do with this? is fthere some sort of feedback loop where the opti is out so the coil won't fire or something? Help me diagnose this problem, please.

 

if you are not getting spark out of the coil to the opti, then check for 12 volts to the coil, if not check icm, and check ignition fuse, start there dont assume opti

 

Sounds like you just got the opti wet, but as stated above, don't go replacing opti's unless you're 100% sure that's the issue.

Do you have any SES codes? Lo-REs Fail?

 

no ses light. Sorry, what is Lo-REs?

 

Lo-Res Fail = Opti is fried.

Have you been able to check your wiring? Just to make sure that the Coil is getting power?

It's fair to assume that your wet opti can be the culprit here, but for the amount of work involved with removing it, you're better off troubleshooting the electrical stuff first.

 

Why would the car run fine for 5 days, then just die, though?

 

find the problem first then when its found you may know why,
like maybe while things were wet they were still making contact but as they were drying corosion started and now you probably have a bad connection somewhere,

so what have you done so far to diagnose this?

 

The corrosion explanation sounds plausible. All I've done to diagnose this so far is find out no spark to coil, curse alot, then take it to the shop, in that order.