Octomine

Octomines are a black, explosive member of the Octorok family found solely underwater. They are covered in spikes and lack arms, and as such can only move by pushing water through their large funnels.

The Legend of Zelda: Phantom Hourglass
Octomines debut in The Legend of Zelda: Phantom Hourglass, where they appear as the primary obstacle in the Salvage Arm minigame. There are two types: a sleeping, blue-eyed type that holds perfectly still in the water, often grouped around Rupees, and an active, yellow-eyed type that moves across the screen sideways back and forth or upward. Due to moving via pumping water, they hold still part of the time while they inhale, and the water blown out can cause the Salvage Arm to swing wildly. On the trip back upwards, the Octomines will appear in the same positions, though the ones that moved across the screen sideways will now do so from the other side. Touching an Octomine will cause it to turn red and explode, causing the Salvage Arm one point of damage.

According to Hyrule Historia, Octomines were initially designed to be minions of Bellum (himself considered a giant Octorok during development), indicating a greater presence than in the finished product, where his primary minions are Phantoms.

The Legend of Zelda: Spirit Tracks
In The Legend of Zelda: Spirit Tracks, Octomines have an even smaller role, simply appearing as a background cannon target in the underwater portion of the Ocean Realm, where they swim upwards from the depths and can be shot for Rupees.