Squiddy

Squiddy is a name used to describe jellyfish-like creatures that occasionally pop out of the sea in Phantom Hourglass and Spirit Tracks, although in the latter they only appear in the Ocean Realm. These monsters do not attack like other random creatures of the sea such as Octoroks and Eye Plants. If left alone, they will slowly fall back into the sea.

If hit with the cannon aboard Linebeck's Ship or the Spirit Train, they will shoot up a little higher into the air and dispense a single Rupee. If one is hit enough, it will eventually split into two, and if those two are hit enough, they will split into three. No matter how many times the three are struck, they will not become four. They will not disperse unless Link misses the last one enough times to drop it into the sea. Even if some have been lost, hitting the remaining one enough times will cause it to split again.

"Juggling" three of these monsters with the cannon is arguably one of the fastest ways to earn rupees in Phantom Hourglass, but the initial Squiddy can be extremely hard to find.

Trivia
Whenever Link hits a Squiddy with the Cannon, it will make a sharp jingle-like noise and a sound similar to that of hitting a Gossip Stone.