When you approach a tower of glass blocks that connects the sea floor to the surface, all the blocks light up (as with the night vision effect) instead of just that area.
MCPE-103654
Underwater lighting
Open
3
(Unassigned)
588300
Confirmed
Multiple
8.0
1.16.220.50 Beta, 1.16.210.60 Beta, 1.16.210.59 Beta, 1.16.210.58 Beta, 1.16.210.56 Beta, ..., 1.16.210.54 Beta, 1.16.210.53 Beta, 1.16.200.51 Beta, 1.16.201 Hotfix, 1.18.2 Hotfix
Retrieved
That actually seems pretty realistic. If you put a piece of glass in a tub of water, you can see through to the bottom, and light still shines through, even though its a bit dimmer.
But the whole sea floor lighting up, does not make sense.