The artist's reading of the dev's tweet was correct Enemy Lifebuoy ice cube trays will be sold with the KanColle Ice Festival (the only problem is that they don't actually have holes through the center) http://kancolle-korimatsuri.jp/ (It's kind of weird to put it into the fund it and funded pool because he drew this after seeing a tweet hinting at it already being funded and existing, but I'll put it into the pool anyway)
Lifebuoy Ice TrayGo for something that stays frozen easily when making the red lifebuoy