Egg Bubble
From Sonic Retro
The boss of Tidal Tempest is the third in Sonic CD. As with most of Robotnik's boss machines on the Miracle Planet, Tidal Tempest's boss is heavily tied to the level theme - namely, the Underwater cliché. Sonic starts off chasing Robotnik and his Egg-O-Matic through a maze-like section above the waves. After the hedgehog lands 4 hits during this pursuit, Robotnik will change his route to escape through a previously-sealed passageway; following sends you below the waterline and towards the real boss.
Robotnik summons a shielding ring of bubbles, which orbit the Egg-O-Matic much like in Flying Eggman, the Sonic 2's Metropolis Zone boss. However, there are many, many more than 7 of these bubbles - and they actually help, rather than damage, when Sonic touches them, preventing him as they do from drowning. To defeat the boss, simply keep leaping up and inhaleing your way through Robotnik's gaseous shield, dodging the energy balls he fires as he swoops around the screen. When the bubble shield is whittled away, a single hit to his pod will send the scientist packing.