Regard the dance, all I know about it is from a quick google search but the pose in this post doesn't close to any "shui xiu wu" poses I found out, their dancing costume seem to based on Han's while the one in this post is Manchu's, and the artist's commentary/tag doesn't mention anything relate to "shui xiu wu".
Therefore, I removed the tag, for now.
If anyone insist on using the tag, a wiki with clear instruction on how to use it (without being overlap with very_long_sleeves chinese_clothes) is much appreciated.