The Sea Worm is the fourth boss in Metal Slug 6.
Most of the attacks aren't really that hard to dodge, but the Sea Worm will be constantly changing position, so be ready for a difficult fight. When he appears, depending on the difficulty, he will start off by spitting about 3 to 8 acid spit projectiles at you, so go underneath his head to avoid these. Get away when he stops, though, as he will begin to spiral in a circle off the screen, and if you get caught in the middle, you die. He will reappear on the right, spiraling towards you. Jump on to his body to avoid being skewered by his head. He floats upright, and takes a few more acid spit shots at you. He then twists his entire body around, causing razor sharp wind to appear around each segment.
A well timed jump avoids this. Again, he will spiral in a circle, so make sure you're not stuck in the middle. He reappears on your left side, and will spit a trail of acid spits which goes up and down the stage. Hide under the Big Shiee to avoid this. After this, he just repeats until you get rid of half his life. When he's flaming, he will spiral around the center, firing 5 energy blasts at you. Just dodge over these or shoot them, and finish him off. If you have the Slug Flyer, this battle is made easier/harder depending on your skill.
- The Sea Worm is reminiscent of the Sandworms of Arrakis from the classic sci-fi novel series Dune, but a polar opposite, as this operates in a water environment. Both are also formidable.
- If the player still has the Slug Flyer, the Sea Worm will spit its acid much faster.
- The Worm Mecha from Metal Slug 7/XX resembles the Sea Worm in terms of movement and the ability to move its separate body parts.
- It is currently unknown if the Sea Worm is a combination of a mutated animal and a machine. This is evidenced by the Sea Worm showing smoke emanating from its body after it has been heavily damaged, and that more smoke spews out after its scales become damaged and chipped-off after suffering heavy fire.
- The ship present before the boss fight resembles the Big Shiee, just without its weapons. Some people think that the Big Shiee was attacked by the Seaworm.