An SD card can survive salt water immersion, but the main risk is corrosion on the contacts and internal connections rather than immediate damage to the memory chip itself. The longer salt remains on the card, the greater the chance of corrosion.

If you recover it, rinse/clean the salt off as soon as possible, then let it dry thoroughly before trying to read it. One community suggestion was to use pure ethyl alcohol to help remove salt, then dry the card for a couple of days. In the reported case here, the recovered card had been underwater for almost a week, was rinsed, and then worked normally in a laptop.

So: recovery is definitely possible, but act quickly to remove salt residue and dry the card before use.