I would like to see the whole clip! The poster of the gif images written that it's Mao doing synchrinized wimming, but I wonder if it's 100% sure? Those gifs looked to me like a dance practice session at summer training camp in Nobeyama.
In this montage created by z4mboni:
from 1:55 to 2:05 you can see clips from a similar practice session with current novice/junior skaters.
During the summer camp the most promising young skaters are chosen based on their performance during the entire camp. One of their tasks is interpreting music - they are asked to improvise a dance while the coaches and dance instructors are looking and taking down notes. The skaters wear their names pinned to their clothes, so the dances instructors who might not know the skaters names very well yet can tell them apart. After that they all dance together some routine taught by the dance instructors.
It just looked like a clip from such form of training because Mao is wearing her name on a note that looks hand-written (it could melt in the water, and I'm not sure if synchro swimmers need such a note anyway) and all the young ladies are wearing clothes more appropriate for a dance training than synchro warm-up. Plus, their clothes are very similar to what the young skaters in the Nobeyama clips are wearing.
I might be totally wrong, though!
Swimming is a good exercise to increase lung capacity and fluency of movements, so it could be great for Mao. What's more, there were photos published where Mao was doing a really nice flip underwater - she might have learned it during the sunchro swimming training. I just thought it would be rather surprising if Mao chose synchro instead of normal swimming - it takes a lot of time to practice a synchro routine, and and that time Mao was probably already very busy with figure skating related training and her school.