Water nymphs
The stories tell that two water spirits used to live around Eteläinen kaupunginselkä. One used to notify of any storms and protected people from drowning and other accidents. It might warn fishers by knocking the bottom of the boat so that the fishers knew it was best to get back to the shore. If they left to the shore immediately, they barely got out of the boat before the storm struck.
The other spirit of Eteläinen kaupunginselkä not only notified about storms but also about beautiful weather. By sailing with black sails, they warned about an oncoming storm, and sailing with white sails was an indication of beautiful weather. The fishers trusted their forecasts.