Are the BNC connectors of Gravity DO/pH/EC meters waterproof?

Is the BNC connector on the Gravity Dissolved oxygen meter (SEN0237-A) supposed to be waterproof? It comes with a nut and rubber gasket, but I didn't think these BNC coaxial connectors would be in any way watertight? If they are, just how waterproof are they? The pH meters (SEN0169) and EC meters (DFR0300-H) have the nuts and gaskets too.