https://gfycat.com/ForthrightRedCoot
Skeleton, wither skeleton, stray and bogged mobs will twitch their arms ("dance") if they try to pathfind to you but continuously fail.
After the version 1.9.1-pre2:
Only affects skeleton, wither skeleton and stray.
Occurred in:
Skeleton, wither skeleton, stray or bogged must attack the player, they must also avoid the sunlight.
But the player in exposure to sunlight.When they were trapped on the boat and minecart.
Confirmed for 15w35e