These spirits resemble giant goldfish with only one big eye instead of a face. They are seen for the first time in Night Alone swimming in a pool full of water, but after draining the pool it is revealed that they can swim in the air just as well as in the water.
These spirits just swim about in their territory. They don't care about the actions or presence of the girls, so they will ignore them and not give chase.
Mythology and Theories Edit
It is possible that these Spirits are in fact the Spirits of people (students or teachers/faculty members) who have drowned in the Pool. The bulletin boards in the School mention how there was a drowned victim in the Pool. Furthermore, you can find a Torn Swimsuit and a Wet Bone in the Pool, which suggests that they belonged to the said victim.