Minecraft 1.13-pre8, Minecraft 1.13-pre9, Minecraft 1.13-pre10, Minecraft 1.13
Java 1.8.0_161 64bit
AMD FX-8370 Eight-Core Processor
NVIDIA Geforce GTX 970
While a player is in the swimming animation, they can't stand when a "walk-through" block is occupying the block above them. Attempting to stand will result in the player floating up. This goes for all waterlogged blocks that the player can stand in: signs, fences, trapdoors, iron bars, glass panes, and conduits, but not sea plants or sugar cane.
However, if the player swims into a space where there are non-waterlogged blocks with a "walk-through" block above them, they will experience
MC-132064 in full force until the non-waterlogged block occupying the space where their head should be is exchanged for water, air, a sea plant, or sugar cane. At this point, the player will immediately stand. However, this can't be achieved with another block, even if that block is waterlogged (except sea plants or sugar cane).