I would by lying if I said it was on the same day and the very different weather makes it obvious, but about 3.5 hours after her departure from Station Pier she is about to pass through Port Phillip Heads at the mouth of Port Phillip Bay. Depending on forecast demand, she sails once of twice a day to and from Devonport. While her single sailing day times are firmly planted in my head, seeing her at very different times on double sailing days does my head in.
The path for ships through the naturally shallow bay is tightly defined and is dredged. The gap between Point Nepean and Point Lonsdale is known as The Rip and it is a narrow passage and very treacherous. The passage was was exploded apart a few years ago to allow ships with a deeper draught to enter the bay. While government authorities deny it, the popular view is that it has drastically changed some beaches and almost taken away the Portsea Beach, which is quite ironic as it is location for rich people's holiday houses, that is those who probably benefit from larger ships coming through The Heads.
Here is a simple map of Port Phillip Bay from Wikipedia, clearly showing places I have mentioned and you can see how narrow The Rip is, and during tidal changes a huge amount of water flows through The Rip. With the exception of the Spirit of Tasmanian, a quite small ship, every other ship passing through The Heads needs a pilot boat. The pilot boats zoom out from Queenscliff to meet arriving and departing ships and travel along side of them. The Port of Melbourne is Australia's busiest port, so there is lots of work for the pilot boats.
You can refer back to the map when reading subsequent posts about our little Easter holiday. We stayed in Point Lonsdale.