Metroid: Zero Mission - (GBA) - Boss #2: Acid Worm
6'Acid Worm' is the second boss in 'Metroid: Zero Mission' for the Nintendo 'Game Boy Advance', released on February 9th, 2004. Acid Worm is found in 'Kraid', the fourth area in the game, in the order of areas discovered, shortly after first activating the carrier system.
Defeating it is fairly simple if you know how to read its moves. In the first phase, Acid Worm will initially stay in the acid a few moments. When you start to see it wiggling, that's the sign that it's about to attack and lunge at you.
There's no way for you to dodge it quick enough on your own. What you need to do is jump up and activate the carrier. It will drop you on the other side, while Acid Worm is stuck onto the platform you were just on. Quickly turn around and fire off a handful of missiles.
As it receives more damage, it will change color and look more withered. At this point, it begins the second phase. The only difference here is the acid water will rise momentarily before receding again. It will lunge at you slightly faster here also.
Keep it up and it will go down.