!Hikari Kohinata "Pikari"
-->'''Voiced by:''' Creator/EriSuzuki
* GenkiGirl: So much so it`s where she got her nickname.
* LivingEmotionalCrutch: Acts as this for the very shy Dotty at times, though when Dotty is made aware that she's using Pikari this way she starts to grow a backbone.
* TheWorldIsJustAwesome: There is nothing in this world that this girl does not enjoy.

!Futaba Ooki "Teko" ("Dotty")
-->'''Voiced by:''' Creator/AiKayano
* AffectionateNickname: "Teko" is a name Hikari comes up with when first getting acquainted with her. based on a comment about her eyebrow thickness ("a tenth of the average thickness").
* AudienceSurrogate: She is the one usually getting all the diving stuff explained to her and for those in the audience with no diving experience.
* CameraFiend: During most activities she can be seen taking pictures.
* ClingyJealousGirl: A light example towards Pikari.
* [[spoiler: ImportantHaircut: At the end of the manga, she cuts off her long hair as a way of letting go her past as a ShrinkingViolet]].
* TheLoad: She is the only member of the diving club without an Open-Water license and at first doesn't even know how to swim.
* TheWatson: When it comes to diving

!Katori Mato:
-->'''Voiced by:''' Creator/ShizukaIto
* CoolTeacher: Tells her students to have fun as much as possible, and it can be hard to tell her apart from her diving students
* GenkiGirl: While being in her early twenties she can give even Pikari a run for her money.
* HotTeacher: Does not seem to be much older than her students, and quite a bit of fanservice comes from her.
* SenseiChan: Normally a responsible adult, but she can be pretty childish sometimes too. Like, getting really into a race across town, bending the rules of a children's game so she wins, and not wanting to pay her debts.
* SternTeacher: She is very strict when it comes to actual teaching, bordering on sadist, especially when teaching diving.
* {{Transplant}}: She seems to be the same character from Amano's older manga ''Roman Club'', where she is the main character's older sister.

!Ai Ninomiya
-->'''Voiced by:''' Creator/SaoriOonishi
* CatGirl: Not really, but she does tend to act and look cat like. Her FaceFault is even a PlayfulCatSmile
* CoolBigSis: To the point that everyone refers to her as Ane-san, or Big Sis
* DCupDistress: Has problems with her size such as having to wear multiple swimsuit tops and accidentally giving a show when buttons pop.
* KickChick: When mad or annoyed (or just for the heck of it) she'll kick her brother. Often it's a flying kick.

!Makoto Ninomiya
-->'''Voiced by:''' Creator/YuichiroUmehara
* TheStoic: Unlike the easily excited girls and teacher Makoto tends to be the calm voice of reason.