Thoughts on pairings/contests:
Yumi v Tsuneyo -- I don't see a way Yumi cares enough to win this. If anything, if she pretends to put her all into it and loses, it may cause some of the class to feel safer around her (knowing Tsuneyo can take her down at-will). Also, Tsuneyo is going to take this very seriously, and quite likely literally. Verdict: Yumi dies. Briefly. Nobody actually notices.
Chika v Uta -- Chika shows up in strategically placed dental floss. Uta slips into hyper-competitive mode and and changes quickly into her Birthday Bathing Suit. A fight breaks out, Yumi jumps in to defend her friend, Tsuneyo jumps in. Yumi dies again. Briefly. Nobody notices again.
Ayane v Yasu -- We don't hear from either of them again until search parties are sent to rescue them in the final chapters.
Sana v Otoha -- Otoha is creeped out by the contest and doesn't try. Wins anyway.
Makoto v Kirin -- Makoto understands the assignment and actually fishes. Kirin misunderstands the assignment, assumes "fish" is sexual, and wins a side-contest instead.
Miku v Io -- Io actually builds a raft. Miku points out that since she's flat AND a swimmer, she IS a raft.
Rin v Molly -- Unmitigated disaster on both accounts. Does not burn down Kumon-Mi thanks to being on the beach. Everyone dies from food poisoning. Briefly. Nobody notices.
Futaba v Nodoka -- An entire scene expanding on the Upside Down House Expanded Universe.
Ami v Touka -- See my previous prediction about Ami finding out about the apartment and stabbing Touka 23 times. Touka dies. Briefly. Everyone notices
Maya v Noriko -- Ami flays the skin off the winner, who spends the rest of the reset without any skin. She still attends classes. The girls begin to realize something might not be completely normal about their high school experience.