This round is very straightforward. Fall into the water and paddle beneath the ice. When you reach the pot grab the red potion from it, then return to the left and take the upper path. Watch out for birds when jumping. The sawfish will try to drill up through the ice to hit you, but they shouldn't be too much of a problem as long as you keep moving. When you reach the end you'll see a door. You can melt the ice and swim to the right for a secret door if you wish, but both routes are the same. Either way, head to the far right and hit the left pot for some loot (hitting the pot to the right will make the loot pot disappear). When you've got all the loot hit the other pot for the key, then go through the door.
This round is very straightforward. Be careful about using the jump-attack as it can't be stopped and you'll end up in the water, so only go in the water when you have to. When you reach the end, fall into the water and break into the area with the door.
In the next area, head to the far right and grab the fire potion. Use it on the ice and swim to the right. When you surface hit the pot to the right first as it contains loot, and hitting the pot to the left will make it disappear.