Kalidus Channel is divided at two parts. The reason why is that more than half of the level is underwater, but you can't go there until you have a certain relic and enter through another way. Because you don't have the required relic, if you jump in the water, you'll just float. Focus on jumping between boxes and rocks attacking all the enemies that gets in your way.
Saving the first Villager: Jacob
About halfway you'll find another man frozen in a large crystal with the Torpol glyph above him. Absorb it. You have freed Jacob. Although he doesn't give you side quests, he runs a shop for you to buy stuff with. Now with him saved, continue right for a save point. Save. Then keep on going til the reach the end of this dungeon. Leave the dungeon.
Back at the travel map, the blackened icon is now revealed. You can now go to Minera Prison Island. (I recommended saving back at Wygol Village before continuing on to Minera Prison Island. There's a reason why). Buy whatever you need and go to Minera Prison Island once you're done.