In seed -6196617772566608530 at 47,33,257 several columns of the ocean floor consist only of sand and gravel, so they fall into the cavern and flood it as soon as the chunk generates.
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In seed -6196617772566608530 at 47,33,257 several columns of the ocean floor consist only of sand and gravel, so they fall into the cavern and flood it as soon as the chunk generates.
migrated
(Unassigned)
Unconfirmed
Minecraft 1.8.4
Retrieved
This is a "feature" of world generation.