When modifying the data of a shulker using a command such as {color:#ff0000}data modify @e[type=shulker,limit=1,sort=nearest] Color set value 16{color}, the shulker is unable to teleport away from the water.
It continues to attempt the teleport, which plays sounds, and it may succeed in changing its rotation, but it will be immediately pulled back to its location in the water.
This may affect them outside of water as well, but I have not tested it.
The game log output produces nothing of note, and the debug profile is attached.
Update: Through further testing, I've discovered that this seems to affect all mobs and goes further than just teleportation. I've reported it as MC-183450.