The bug
If you place down a translucent block and position a boat directly against it, the block will not render through the inner part of the boat.
Affected blocks:
Frosted ice
Ice
Slime block
Stained glass
Tinted glass
Nether portals
Stained glass panes
Honey block
How to reproduce
Place down a boat
Use setblock or pistons to put an ice block into the middle of the boat
Observe that the part of the ice block that is inside the boat fails to render
Fixed cases
The following blocks were previously affected by this bug, but no longer are:
Banner, Bed, Chest, Conduit, Ender chest, Entity head, Shulker box, Signs, and Trapped chest.
Linked issues
is duplicated by 2
relates to 13
MC-248995
Boats do not block the rendering of seagrass, kelp and corals
Open
MC-188768
The inside of a boat blocks the rendering of nether portal blocks
Open
MC-229405
The inside of boats blocks the rendering of most translucent objects with the "Improved Transparency" option enabled
Resolved
MC-47636
Boats appear to be sunken in water
Resolved
MC-114486
Boats break anaglyph 3D on held items, transparent blocks, and the block outline
Resolved
Attachments
Comments 12
Partially fixed in some 1.15 snapshot; block entities are no longer affected but transparent blocks still are. Conduits in particular have the water affected but the conduit itself not affected (which is intended behavior, since water is supposed to be culled).
This is caused by the invisible layer used to hide water in boats.