There are two channels in and out of Halifax- the eastern channel and the western (also known as the deep water channel.)
Most ships take the eastern channel since it is pretty much a straight run. Using the western channel involves making a dog leg course.
When a ship is inbound it invariably takes the eastern channel. If ships are leaving at the same time, and do not wish to crowd the inbound, they take the western channel.
It is not unusual to see a ship taking the western channel, but to see four of them do it at once must be a bit of a rarity.
Today's arrival of the Algoma Guardian was so timed that there were four outbounds during her passage. The bulker Good Luck, container ship Hoechst Express, cruise ship Norwegian Spirit and the supplier Trinty Sea [ in that order] ended up taking the western channel. This resulted in a higgelty piggelty sort of look as they made the dog leg.
In the photo, Good Luck is in the lead and has completed the last section of the dog leg and is heading striaght outbound. Hoechst Express and Norwegian Spirit are on the last part, and Trinity Sea is still on the first part of the dog leg.