"Firs' years, this way!"
Never thought you'd hear that again, did you? This time, though, the familiar call seems to be nothing more than an echo, as the groundskeeper is not actually keeping watch over the little boats tied to Hogwarts' dock. Perhaps the Hogwarts staff feels that their newest graduates are more than capable of sending themselves off?
The same fleet of magical boats that carried you to the school as a firstie still bob gently on the dark, deep lake, waiting for your departure. Two graduates per boat, please, and be careful not to tip over. The boat will take off once you release its rope from the dock.
Enjoy your last trip across the Black Lake, and be mindful of Barty.