So my 06 G35 Coupe got into a couple puddles last weekend. Car was started for about a minute after that to be parked and oil pressure came on, didn't think much of it usually it'll come on if it gets damped. but checked oil anyways and it was fine.After about two hours I turned it on again so I can go get new air filter and cabin filter. Left it running in the auto-zone parking lot as it was going to be a quick in and out, came out to my car being on but engine stopped running, tested for fuel pressure, spark, NONE. Also plugged in OBD but it was not connecting to ECU. I changed the IPDM this weekend as found a couple port and relays extremely corroded but that didn't do anything. Disconnected the anti-theft module and didn't want to start after that either. Im at my breaking point, dont know what it could be and I'm about to just junk it. Don't want to as I had a ton of parts ready to go on.

Sounds like you blew something in the fusible link, I'd start there.