The following is an in-depth guide for the ninth area of Metroid II: Return of Samus.
Here go up the shaft to the very top, then go left. Here, go all the way left to the shaft at the end, go up, and go all the way right to the other side, go up, and go all the way left to the other side and the go up. Here, go right, spin jump up out of the ceiling. To get out of the water, you'll need to space jump. Go all the way to the right side of this big room, use your spider ball and stick to the walls and go around. There are three halls in the top, one has a heal pool and a missile pool, which is pretty much necessary, the second one has an Ice Beam which you need to grab if you don't have it already. The third one let's you move on. Go up the third one once you're ready, go to the top and go left. Go to the top of the next room and go into the ceiling to go across. You know have 8 more metroids to kill, but don't worry, they're all easy and in a straight line. These Metroids can be killed by being frozen with the Ice Beam and then quickly killed with 5 missiles. Go to the right of this room killing the metroid in the way. In the next shaft there's a metroid to kill. go to the top and go out to the right. In this next shaft, there are two metroids to kill. Go to the top and go to the left. In this room there are two metroids to kill. Go all the way to the left to the next room. In this room there are two metroids. Go to the bottom to kill both of them. At this point, you should go back to the heal pools to heal your missiles and health, emphasis on missiles as you're going to need them for the final boss coming up. Anyways, go right at the bottom of this room. Here, go all the way to the right of the room and drop out of the edge of it to face off against the final boss, Queen Metroid. This fight isn't that bad, don't worry. Stay in the lower right corner of the screen at all times, whenever the queen shoots her head at you, react quickly and spam your missiles as fast as possible. After you shoot 150 missiles at it, (won't take that long if you spam fast enough,) the Queen Metroid goes down. You now have a mini metroid following you that can destroy blocks for you. Go all the way to the left until you can't. Repeatedly Go up and then right until you have to go left instead, go left and then all the way up to climb out of the hole. Space Jump towards the right wall to get onto the ledge, then fall off the ledge onto the right to find your ship, climb inside to end Metroid II: Return of Samus.