How do minimize salt water corrosion on jetski?

The best way is not to ride in salt water. But if you do ride in salt water, you need to clean the jet ski thoroughly after riding it.

Rinse off the entire jet ski. Thoroughly rinse the intake areas. Flush the jet ski following the procedure in the operator's manual (to get the salt water out of the engine cooling paths and the exhaust system). Remove the drain plugs and wash the bilge. Then spray a light coat of oil over exposed metal surfaces. If the jet ski is going to be stored for a while, spray fogging oil in the air intake while the engine is running.