i just finished playing and as someone who LOVES a good medaphor i desprately want to give my two sense on this so i hope you dont mind what might be a long ish reply
i think the "rot" (or when everyone started decaying mentally and physically) is a metaphor for junes friends slowly starting to change, and in turn noticing how june wasnt.
from an outsider prespective it was clear to me how alot of the "joking" her friends were doing (for example when McCoy was sad that june wasnt the last to get there, and when he called her lazy) was actually serious.
ryan is the only one who seems to genuinely care for her, and i think him leaving his jacket behind for june is representing that, but i also think that him not being able to swim is representative of him not being strong enough to leave with june. he wants to, but in the end he cant.
alternitively, june is aware of her boundries, aware of what makes her feel comfortable- and more importantly what makes her feel unsafe. in the ending where she follows them into the sea, ryan holds tighter onto her hand. i think this represents how she desprately wants everything to just go back to the way it was, and uses trusting ryan as an exuse to stay with the people who are pushing her away, hoping that everything will go back to normal eventually.
and what really hits home for me is that: the only thing keeping her there is fear. she knew she was in danger, she knew everything around her wasnt right, she knew her friends were acting the way they were acting, but it was the trust she has for them that made her want to stay. she trusted that this wasnt actually them, that there was something wrong and if she can just get them off this island then everything will go back to normal,
and it was only when there was a real threat, when she was physically being away in a way that she couldnt deny anymore, that the trust was stripped away and left only her fear of being abandoned. it doesnt matter who shes with at this point- as long as shes not alone.
in the ending where she swims back up, the fog horn goes off. this implies that she saved herself. she realized that her friends werent her friends anymore, and that she wasnt willing to drown herself for them. she loved them- still loves them. her leaving them doesnt change that, but its better to leave someone whos hurting you then to stay with them becase you love them. sometimes all you can do for someone is hope for them.
i think its important to note that this does not mean that these people were never her friends. people grow, and people change. and sometimes the people who care about you are changed in ways you cannot help, and you want to help them- save them, but sometimes they dont want to be saved. and theres nothing you can do but save yourself.
i think the reason im so drawn to studio investegrave games is how narritively focused they are: rarely are their games ever about whats pysically happening- thats why they dont explain whats bringing everyone to the sea. becase it doesnt matter whats at the bottom, it matters what it represents.
thank you for coming to my ted talk about why SIG games are my favorite genre of games. oh my gojdjfdk i spent like two hours on this reply im gonna go pass out and vividly swirl this game in my head now.