the smallest opening.
The smallest holes can hold a sea.
“little hole” belongs to the early period when a cute nickname, a sea creature and a terrible idea could all live comfortably in the same couplet. Its fish-world romance sounds ridiculous on purpose. A jellybean can be an object of affection; an orca can apparently be romantic. Nobody is calling a marine biologist.
The title works because it keeps changing size. It can be a silly double entendre, a tiny opening in an enormous world, or the kind of absence that grows larger the longer somebody looks at it. The joke does not stop being a joke when the darker reading arrives.
That is also why the song feels at home in the live Crab Park world. There is room for an interrupted performance, an audience laughing at the wrong moment, or a small ridiculous detail taking on a life of its own. Not every ominous image needs solemn music to carry it.
Some holes let the water in. Some let something out. This song is not especially interested in making that distinction easy.
Is the title meant to be funny?
Very much so. It would be a shame to build an entire ocean full of monsters and then refuse to make one stupid joke about a hole.
Why does the cute imagery start to feel stranger?
Because “small” and “harmless” are not synonyms. Sometimes the gentlest way to introduce a frightening image is to make it adorable first.