To reproduce, construct a platform of bottom slabs underwater and swim on it.
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To reproduce, construct a platform of bottom slabs underwater and swim on it.
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Minecraft 18w07b, Minecraft 18w07c
Minecraft 18w11a
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Slab is air-type block. Water above is water-type block. When you swim - your head is in air. When you stand up - your head is in water. Another reason to make new water-type slabs "submerged_slab".