As the name suggests, this is the first ice level in the game, taking place in Arctic conditions. Like the previous level, you start surrounded by sharks; these Arctic sharks are tougher than those found in the Open Ocean, taking several hits to defeat. Fortunately, they will move away after a few seconds, and you should be able to avoid them fairly easily.
The layout of this level is confusing, and its inhabitants are deadly: As you dive into its depths, you discover that sharks are not the main threat; instead, it is the terrifying Arctic spider crabs. These crabs will pounce at you from their hiding places and aggressively pursue you. The simplest way to defeat these enemies is to use the Charge Sonar attack (by pressing the Dash and Sonar buttons simultaneously); this will kill them instantly.
Fortunately, if you know where to go, this level is also very simple: In the water section in which you start, there is a Barrier Glyph, and you need only get past it to complete the level. To find its associated Key Glyph, you'll need to make your way across the land to the left of your starting point. Unlike in previous levels, Ecco can slide and bounce across the ice sections that separate the waters of this level. By timing your jumps, you can bounce over the many holes in the ice.
Using this method, you should look for a pool containing fish to the left of the starting area. This is the only source of health in the level, and you should use it to heal if you have been injured. From here, you will need to move left again, bouncing over the next pool and diving into the one after it. Here, you will find a cavernous area; as you go down and to the left, you will discover the Key Glyph amongst the many enemies within. Dash into it, and make your way back to surface. Return to the fish pool, healing if you need to, then head right to the area in which you started, going down and right to find the Barrier Glyph. Use your Sonar to get rid of the Barrier Glyph, and move into the area beyond. The end of the level is guarded by several Arctic spider crabs, which you can dash past, escaping to the next level.