Is Jack Dead?

If you haven't read Chapter 821 yet, do it now and then return to this thread.

Spoiler: Jack - Chapter 821

In chapter 821, we see Jack and his fleet being destroyed by Zunisha. Later that chapter, Apoo confirms that the communication to Jack was lost.

Now we can all agree that Jack won't be killed by Zunisha's blow alone, but: Jack is a Devil Fruit user! With all ships destroyed, his underlings probably all out cold, and Jack falling into the water, the situation looks very bad for him. So we must ask:

1. Is Jack dead?
2. If not, how will he be rescued?
   

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Spoiler: Possible Solution

This situation is similar to the last time Jack was defeated, by Sengoku and Fujitora. The Marines thought Jack drowned, while in fact he somehow survived/got rescued and made his way back to Zou. Will he be saved in the same way he was saved last time? The main idea here is that a 2nd Calamity, inspired by the sea monster Leviathan, will save him. Possible?