One of the realities about Halifax harbour is fog. Even with relatively warm air temperatures, the ocean remains cold. At time of writing the Herring Cove smart buoy just off Halifax is reporting air temperature of 19.7C and sea surface temperature of 12.4C. With very little wind (7.8kts) and high relative humidity (approx. 100%), conditions are ideal for fog.
Once the ship was in past Ives Knoll it became fully visible even though Macnab's Island in the background was still well fogged in.