Inspired by this gene here: There's a lot of suggestions for having more diverse aquatic habitats, I don't remember reading anything about this but correct me if I'm wrong  Anyhoo, this would be a new ability and food source. It would essentially be an underwater equivalent to the insect collecting. The plankton would appear in spaces underwater and would look and work like the swarms of flies in swamp islands, only instead of moving closer to your nichelings each turn they would move