I can confirm this issue and the dirt blocks are also spreading and destroying the area.
There are also other weird things going on
I can confirm this bug, it seems to happen at biom edges.
Placing a boat on water --> sink.
Placing on solid block --> swim.
I also hope this is a bug and not a feature.
I think it's different, I know it from 1.12.2. where light updates can be forgotten, after a block update the light level is correct.
Not so in this case with, where ~20 blocks away from a torch the light level changes from 0 to 15 while the next block stays at 0.
I forgot to say:
Iit's persistent.
It's saved.
And with blockupdates at the borders it spreads.
Test 2 another PC fresh snapshot download
Seed 54321
Position 280 / 63 / 10
does not happen always and everywhere
best results with night + deep ocean + gravel
New World generated seed: 12345
Found deep ocean at -2196 / 63 / -1096(optional) set time night
look at ocean ground
place torch
remove torch
look at ocean ground
@ Kumasasa
Versions 18w19a&b were unplayable for me it freezed after short time and I had to kill java via task manager.
Versions 18w20a&b were also corupting my worlds with chunkloading problems.
After deleting the corupt region file 18w20c works fine with my 18w20b world.
I think my first pictures are not spectacular enough
I have the same issue (updatet from 18w16a) and I also understand that things in snapshots will come and go.
But I think it would be a better solution for future releases, if "underwater things" are removed or changed they should be replaced with water instead of air.
Jepp! ... and don't go to the Nether.
It looks like something was wrong with his birthdaycake 😃
I had the same issue.
seed: 18w47a (1458142478)
location: next to my spawn at -181 68 61