Submarine Eggman II (サブマリンエッグマンII?) is the seventh boss in Sonic the Hedgehog 2, that the player has to encounter at Oil Ocean Zone. The player has to do eight hits to defeat submarine mobile, that is piloted by Dr. Robotnik.
Unlike its counterpart from Hill Top Zone, this version of Submarine Eggman looks like a submarine-bullet-like machine. It has black and yellow stripes, as well as yellow bottom and side headlights. It is also known to have two different attachments for different attack techniques.
Dr. Robotnik begins the battle by emerging from the oil. When the player gets opportunity to attack into to the Submarine Eggman II, Dr. Robotnik quickly sinks back down into the oil and then, he fires an air-borne attack spear at the player which can be avoided by jumping.
Its second separate attachment with a gun will appear and fire three shots. While its three shots can fire at random heights, one of its shots may temporarily ignite the entire platform on blue fire. After this Dr. Robotnik will rise out of the oil again and the process will repeat. Like all Sonic the Hedgehog 2 bosses, Submarine Eggman II takes eight hits to be defeated. The player can then head to the capsule to complete the zone.
- During the boss encounter, the full form of Submarine Eggman II cannot be viewed from the oil and none of its add-ons seem to be fitted on his mobile, but it is possible that both of attachments are possibly attached to the submarine with long chains. They could also come out of the hatch on top of the submarine. The fully seen sprite is seen on the right.
- Eggman's sprite in the cockpit is different from it's normal appearance, except for when he has been hit and defeated. He looks back and forth a couple of times before submerging again.
- If the player does not attack on the Submarine Eggman II when it slowly raises and goes back down into the oil ocean, Robotnik will not send the airborne spear, but instead skips it to the gun attachment.
- Unlike Submarine Eggman in the Hill Top Zone, Submarine Eggman II is never shown with the ability to fly (i.e. to lift itself out of the oil).
- There is an extremely easy way to defeat this boss. If the player stays under a platform after attacking, then neither the gun nor spear can hit Sonic, then when Robotnik resurfaces the player can continue their attack. Sonic/Tails will sink to the oil and die unless the player keeps taping A/B-button constantly.
- Despite the logic when chemical reaction such as an explosion can cause the oil to ignite, the destruction and explosions of the Submarine Eggman II does not cause this.
- In the 2013 iPhone remake of Sonic 2, the refinery towers in the background are made more visible.
- In the easy mode featured in Sonic Jam, the Star Post is moved from the top of the oil slide to somewhere closer to the boss battle arena, making it harder to miss.
- Submarine Eggman II is also one of three bosses in Sonic the Hedgehog 2 that is still featured in the same easy mode. It only takes three hits to defeat it.