Buttons act as slabs and although they can be placed in a water source block they block flowing water which shouldn't be how they work since levers, repeaters, and comparators all allow water to follow over them and buttons should work the same way. It will also be much more useful for redstone
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It appears that you copied an existing open report (MCPE-32488).
Please do not create duplicate reports.
Duplicate of MCPE-32488, it looks copy of pictures