Hi Carl;
First a few questions;
Was it salt water?
How long was it under and at what depth was it at?
Many of the systems are closed for the engine:
Drain all fluids and replace them;
remove and replace all filters
remove battery
wash engine compartment with a product called Scrubbing Bubbles orange.
wash with clear fresh water.
Put body on jack stands and remove interior including door panels and head liner, pull all drain holes.
If there are signs of mud or muck, wash it all down.
use fans and hair dryers to blow-dry everything, use compressed air if available.
Unplug and inspect all connections.
If your interior was in good shape, it may be salvageable, but it all has to be removed from the seat frames and dried out.
NOTE: drying everything out and cleaning it will prevent mildew and mold
Remove tires and clean.
once everything is dry, inspect for damage, replace things as necessary. If there were problems before then plan on them still being there. If it ran well and the engine was closed up, then chances are changing the oil and filter will be enough. If you find water in the oil, then open the cam cover and inspect for corrosion.
Aluminum will corrode just like steel, water will cause exfoliation over long periods under water. a couple of weeks should be ok if it's cleaned. If the stator (looks like the flywheel) side of the engine looks to be showing signs of corrosion, clean it and dry it well.
unplug and test for grounds.
Remember, you can put your computers key board in the dishwasher, dry it off well and plug it in again. You just have to make sure all connections are moisture free.
Bill