I have been playing in the 1.14 snapshots since yesterday (Started world in previous snapshot, moved it to 18w47a just minuets ago), had just gone to the nether, and made a nether wart farm. 100 blocks south of the nether wart farm, above an ocean, I found my nether warts without the soul sand floating above the ocean. As I moved closer to the floating nether warts, they all popped into items and fell except for one. Then I noticed that water blocks were "breaking" nearby, as can be recreated by using "/setblock ~ ~ ~ air destroy" while standing in water. They showed water breaking particles, as if they were actually being broken. I do not know if any of these things have any relation to each other, but they accrued in the same spot.

The below screenshot is of the last floating nether warts and a water block breaking.