Sugarcanes can be planted underwater

That is just strange...

Thank you for your report!
However, this issue is a Duplicate of MC-929.

If you have additional information, please add it to that report.
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Yeap.
Underwater sugar cane doesn't break → MC-929 - Underwater sugar cane.
Sugar cane can't be waterlogged → MC-125351 - Some blocks still show air around them when surrounded by water/cannot be waterlogged.