I'm sorry, but I would contend that if you actually got salt water inside the HD, then I really don't see how you can get the salt out by rinsing it out. On the other side of the breather hole is a fine filter designed to keep fine particles out, equalize air pressure and stabilize humidity. You get the drive wet, the filter will get saturated and eventually the salt water will penetrate the filter with a relatively small amount of dissolved salt. I doubt that more than a few drops would get through but that is plenty enough to coat the interior with some salt crystals. Rinsing the drive with distilled water is not going to be able to get rid of the salt on the inside because you are not going to be able to get enough distilled water inside to use as a solvent.
Even if you could get enough distiled water inside, baking won't help because the distilled water would just evaporate leaving the salt behind. You have to rinse till there is NO salt left by draining water out through the filtered breather hole till there is no salt inside and that is going to take a very long time because it is only going to allow very small droplets through. Once no salt exists then you can bake.
If the data is valuable enough, the drive needs to go to a data recovery center, un-altered: Don't even try to do anything, just leave it to the professionals for your efforts will just complicate theirs. If it isn't valuable enough, then clean what you can externally and hope for the best internally when you power it up.