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In Harry Potter and the Sorcerer's Stone, we see Harry and the rest of the first-years riding boats up to Hogwarts when we're first introduced to it.
According to the wikia (emphasis mine):
The Hogwarts boats are traditionally used to transport the first year students, accompanied by Hogwarts gamekeeper Hagrid across the Black Lake from Hogsmeade Station to the castle at the start of the school year. At the end of the school year, first years take the boats back across the lake to Hogsmeade Station.
During the Hogwarts graduation ceremony, the seventh-years ride the boats back across the lake as they leave the school for the last time.
So Harry and Co would take a ride both to and from Hogwarts at the beginning and end of their first year, and the graduating class gets one last go as well before leaving.
What is the significance or meaning of these boat trips? Who started this tradition and why?