If you look at the picture, you can look through the empty space of the phantom's wings and see the seafloor without any water. This is the same bug that happened with particle effects before the new lightning engine was released.
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Thank you for your report!
We're actually already tracking this issue in MC-9553, so I resolved and linked this ticket as a duplicate.
However, that ticket has already been resolved as Fixed. The fix will arrive in the next version or is already included in the latest development version of the game.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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