I'm not sure if the footage could be recoverable otherwise?
While the card itself might be unusable due to salt water destroying the tracks on the circuit board inside, the chips themselves reside in sealed airtight packages. They have a pretty good chance of surviving at least a short time in the drink.
As long as the leads on the chips aren't too seriously damaged, if you were to transplant the chips (flash IC(s) + controller) onto a new board in a new card, you'd have a fair chance of recovering the footage.