I did about a dozen water crossings last month through the Cape. The only time water came in was when I got bogged in a crossing. It filled up fast! I was in about 3 feet of water for around 60 seconds before I was snatched out, engine running. Some people were putting duct tape over the door seals for extra protection, which seemed to help.
I used a car bra (highly recommended) for all crossings which helped a lot to keep water out of the engine bay as well as a healthy spray of WD40 on the engine before each crossing and dielectric grease on anything electrical I could find. I also wrapped all of the coils and any other switches/connectors in electrical tape before I left.
The carpet has dried out now and luckily I haven't had any electrical problems as a result (fingers crossed it lasts!).
Water crossings are not something I go looking to do, but they are a part of where I live so it helps to be prepared.
