Squiddy

Squiddies are passive, flying jellyfish enemies in The Legend of Zelda: Phantom Hourglass and The Legend of Zelda: Spirit Tracks. They are undefeatable, but attacking them repeatedly can give Link potentially endless amounts of Rupees. They are shaped a lot like a bell, and even make a ringing noise when hit. They are only encountered during vehicle segments, and, like most other enemies encountered during those, are quite large.

The Legend of Zelda: Phantom Hourglass
In The Legend of Zelda: Phantom Hourglass, Squiddies are found in all four seas, where in certain portions one may randomly float up above the surface before gently floating back down. By using the cannon on it, Link gains one green Rupee per hit, while the ringing noise they make gradually increases in pitch. Hitting them also causes them to bounce upward further. After several hits, the Squiddy splits in two and the pitch resets. Up to three Squiddies can be active at a time, and they remain around the ship even if it has stopped. If a Squiddy goes back underwater, it cannot be hit anymore, and as such distractions from other enemies may cause the player to lose track of them.

The Legend of Zelda: Spirit Tracks
In The Legend of Zelda: Spirit Tracks, Squiddies retain their appearance and behavior from Phantom Hourglass. Due to the varying terrain of the game, however, they are only found in the Ocean Realm. If one touches ground, it will poof into light purple clouds. Of note is that in this game, they do not go higher than the maximum height of a cannon shot, so even if one is above the top edge of the screen, tapping along the top edge in its direction will still hit it.