i recall this scene from https://www.mangago.me/read-manga/we_re_still_in_the_spring_of_life/uu/d_chapter-2/pg-18/ but maybe it's not this one
The first BL manhwa that comes to mind with a water fight is Summer Time: https://www.mangago.me/read-manga/summer_season/uu/br_chapter-165229/pg-40/

I’m going crazy looking for this manga or manhwa I read some time ago. It was about two high school boys falling in love but I can’t remember anything from the plot.
The only thing that I remember is that there was they beautiful scene where the two boys had a water fight after cleaning the school.
I’m not entirely sure if it’s a manga because I remember it being in colour but I might be mistaken.
Could someone help meeee