In the fanfiction, George saving Harry from the lake could lead to a series of adventures. Harry might want to repay George by joining him on some quests. Also, it could change the power dynamics within their group of friends. Since George has now done such a heroic deed, the others might look at him differently and he could potentially have more influence in group decisions.
For Harry, his friends in Gryffindor could be a bit confused at first. They know Draco is not exactly a friendly character. But overall, it could lead to a more united front against real threats in Hogwarts. The teachers might also take notice. Dumbledore, for instance, would probably be proud of Harry for showing such selfless courage, regardless of who he was saving.
The wizarding world would be in shock. The Malfoys are known for their dislike of the Potters, so Draco saving Harry would go against the family's reputation. It could lead to Draco being ostracized by some in the pure - blood community.
It's possible that George calls upon some magical creatures that are native to the lake. These creatures could help him in rescuing Harry. For example, he might have made a deal with a water nymph or a group of friendly mermaids. They could have guided him to Harry and assisted in getting Harry out of the dangerous situation in the lake.
One consequence could be that he gains an unexpected ally in Draco. Draco might feel indebted to Harry and start to change his views towards him, which could lead to some interesting interactions between them in the future. This could also cause some tension among their respective groups of friends.
Some fanfictions might depict that the wizarding community might see her as a hero. However, others could show that she faces backlash from some conservative wizards who think she overstepped her bounds. They might try to isolate her at Hogwarts or spread rumors about her. But her friends like Harry, Ron and Hermione would surely support her through it all.
One consequence could be a change in the public's perception of Hermione. Some might see her as a hero for standing up against an unjust imprisonment, while others might view her actions as traitorous, especially if they believe Draco was truly guilty. This could create a divide among the wizarding community.
One consequence could be that Arthur becomes more aware of the threats around him. He might start to trust Merlin even more, seeing him as someone who truly has his best interests at heart. This could lead to Arthur relying on Merlin more in future situations.
Dudley might face his father's anger. Vernon could be furious that Dudley has gone against him to protect Harry.
It could be that when Harry saves Draco, a hidden prophecy is revealed. The prophecy states that their fates are intertwined and that they must work together to save the wizarding world from a greater evil that is yet to come. This forces them to put aside their differences and grudges and form an unlikely alliance.
One consequence could be that Artemis becomes indebted to Percy. This might lead to her providing him with special favors or assistance in his future adventures. For example, she could offer her hunters to help Percy in a battle.