The Northside Reef is where the RMS Titanic, the sharks' Headquarters, is located. Northside is the whole area including the Open, where one of the Titanic residents met his end.
In Shark Tale Edit
The Northside didn't have a name inside the film though, but is briefly mentioned by the alpha of the Great White sharks Lino, when he was having a conversation with one of his members, Mr. Sykes.
It's almost time, that they would run the reef.
–––––Lino to Sykes in Shark Tale(film)
Known residents of Northside Edit
The known residents who live in the Titanic at the Northside are:
• Don Lino
• Annabelle(formally, when she was still alive and living together with Lino)
• Frankie(formally, before he died at the Open)
• Don Ira Feinberg