There is an issue when you column blocks out of the ocean from the bottom to 2 block above water that the chunk you are in lights up on the bottom of the ocean.
Linked issues
Comments 2
Sounds like MC-128299. If not, please do attach screenshots.
MC-130830
Lighting Glitch in ocean that effects one chunk exactly...
Resolved
Duplicate
0
Chad Taylor
(Unassigned)
Unconfirmed
Minecraft 1.13-pre1
Retrieved
Please provide screenshots.