For the final regular level of the ice world, the developers saved the best for last.
Something Fishy
In this level, you're going to be swimming around a lot. You'll need to free the fish, and you'll also need to hit the switch to open the Big Door if you want to activate the exit teleporter.
You'll start out as a fish just like the one from the first level of the ice world. There are some things that we need to do in order to complete the two tasks given to us as well as complete the level entirely.
Shortly after the start, there is a trench you can swim down into where there are some rings. You'll need to swim into all of them and do it really, really quickly before the rings re-spawn, and by doing that, For best results, you'll want to mash the A button really quickly to ensure speed as well as control. You'll get a message telling you that you hit all the rings before the trophy shows up. The trophy will be above the surface of the water, and you'll need to get the walrus later in the level and swim around the perimeter of the level to find and collect it.
You also need to free the fish. The fish will be in glass tanks that can be opened with a nearby switch. One is near the giant skull. Another one is near the giant treasure chest, A third one is past the wall that you need to raise the water level for in order to jump over it. Make sure you hold Up on the Control Stick while double tapping B near the top of the wall to ensure that you don't land on the top of the wall on the way over, because there is no energy to pick up here. If you lose any health in this level, you're not getting it back. A fourth one is above the wall with the number "100" on it to dictate the current water level, and you'll need to raise the water level to jump over this one much like you did that other wall. By freeing all four fish, you'll complete one of the mission objectives.
Speaking of the giant treasure chest, you need a key to open it. The key will be in the igloo near the jelly fish that you can find past the wall with the number "100" printed on it (which is timestamped for your convenience in the Power Cells section), and it is shaped like a fish instead of an actual key. The reward? The four Power Cells that can't be found out in the open.
There is a switch by itself on a column, and above it is a walrus. Swim into the switch to drop a mine on the surface of the water, then move the mine with the Control Stick to hit the walrus. This is the only way to defeat the walrus, and by doing so, you can take control of it and move on the surface of the water to collect a few things.
Near the giant treasure chest is a valve on the floor. Swimming into it lets you lower the water level, and swimming into it a second time lets you raise the water level to be higher than normal. From there, you'll be able to switch between the lower water level and the higher water level. You'll need the higher water level to get one of the fish that you need to free (which also has two Power Cells near it, timestamped in the Power Cells section for your convenience).
There is a big metal door at ground level in the maze, but in order to open it, you'll need to lower the water level so that the area near it is dry, and you'll also need to play as the walrus. There is a polar bear tank on the other side, as well as another one on the ramp. You'll need to take them both out the walrus; using one polar bear tank to get rid of the other is a lot harder and will get you killed. Once both polar bear tanks are defeated, take control of one, as it is much easier to go up the ramp leading up to the switch with a polar bear tank than as the walrus. The switch for the Big Door behind the jelly fish and the igloo and access to the exit teleporter on the other side will be at the top. Hit the switch to open the Big Door so you can get out of the level. From here, you'll want to take control of the fish again, raise the water level all the way up again at the valve near the treasure chest, then get to the wall with the number "100" and jump over it one more time to finish the level.
Power Cells
1 | 2 | 3-4 | 5 | 6-7 | 8 | 9-10 (and one of the fish) | 11 (plus one of the fish and the skeleton key) | 12-15 (need the skeleton key)