Sorry /u/jeb_ if got any of this info wrong. Just going of memory here 😛
Note: these answers arent word for word but it gets the point across.
Q: What was that mystery 5th mob image. Aka mob "E" A: It was just a mock up image. It literally meant nothing.
Q: What is the bubble stream things? What do they do? A: There will be under water ravines with bubbles coming out of them. If you swim over it with a boat you will sink. You will also be able to breathe in them and transport items through them.
Q: Do the bubbles flow horizontally? Can you transport items like that? A: No, it only flows up.
Q: I heard about combat changes, what are the changes? A: Blocking will no longer be with right click, it will be activated by shifting and/or walking backwards. PVP wont return to 1.8 pvp.
Also, the off-hand will no longer be able to be used for placing blocks, mining or attacking etc. It is now only for shields, compasses, maps and items of that nature but you can still hold any item or block in your off-hand.
Q: Did you see the fix for ghost blocks? Will you fix It? A: Yes. We are always trying to fix bugs. (so kindof yes.)
Q: How big is Mob C? A: They are very large. Around 3×3 blocks.
Q: Will there be any loot in the shipwrecks? A: Yes there will be chests with treasure in them.
Q: Are the coral new blocks? It looks like terracotta. A: They are new blocks. The blocks shown was an old texture.
Other Q's to the Mojang ppl and stuff:
Insider info: Mob C was actually green and gray. (or similar colours, hopefully i remembered that right lol)
Your breath bar will not instantly regen.
I may have missed some, so if you have any questions I might be able to answer them. If jeb sees this then he could. So yeah.