Normal chests update so that they fit the underwater environment, however trapped chests and Ender chests don't (see screenshot attachment).
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[media]

Also, shulker boxes are not listed in the #minecraft:water_hacked tag as well.

Probably, it is Work As Intended.

@unknown Chests behaving differently is clearly not working as intended...

It's inconsistent with normal chests.

Still an issue in 18w10a.

The original ticket is still open, please comment on that when you have new info to add.