Unfortunately, salt water gets everywhere and is damaging to electronics, especially when powered up.
Even if you flushed it with fresh water, there may be some salt water that is still in the nooks and crannies still corroding the electronics internally.
If you get lucky and everything seems fine, I'd keep an eye on the Spark as it may fail when not expected.
You can also try the rice bowl trick to remove the moisture but the salt residue will remain and continue to corrode stuff until failure. It may or may not happen?
Good luck.
Even if you flushed it with fresh water, there may be some salt water that is still in the nooks and crannies still corroding the electronics internally.
If you get lucky and everything seems fine, I'd keep an eye on the Spark as it may fail when not expected.
You can also try the rice bowl trick to remove the moisture but the salt residue will remain and continue to corrode stuff until failure. It may or may not happen?
Good luck.