Whoever had decided on an underwater event for the middle of winter, Harry had a few words for them. It was snowing and Harry was very reluctant to shed his thick coat. Mama rolled her eyes and layered another warming charm on him. Sirius ruffled his hair.
"Guys, come on, everyone's watching," Harry grumbled despite his small step further into their family huddle.
"You've got your gillyweed?" Mama continued without any respect for Harry's social status, fussing over him.
"Yes, I've got everything!"
"Mr. Potter! We're beginning soon!"
Harry avoided Sirius' hug, aware of the whole school's eyes watching him. He shuffled over to the other contestants, setting his coat on a bench and double checking his wand was secure in his wrist holster and the knife Sirius had given him secured in its ankle holster. He also had a muggle waterproof watch, and he fumbled over the buttons to figure out how to set a timer. Then he clutched his jar of gillyweed and waited, looking around the stands for his friends. Ron had slept through breakfast, and Harry was a little offended his friend hadn't shown up to wish him good luck before the task. Harry hadn't heard him come to bed either, so he assumed Ron had been up late celebrating his victory. But Harry really hoped he didn't sleep through the whole event.
"Alright, before we begin," Bagman came over and pinned a small, smooth rock to Harry's wetsuit. "We obviously won't be able to see you underneath the water, will we? So we have these scrying stones that we'll use to project what is happening. Now, Mr. Potter," the man paused and gave a nervous, high-pitched laugh, "I have been asked to remind you that committing genocide against the merfolk below is not acceptable. They are an endangered species."
"Of course," Harry said. "I would never." The adults eyed him dubiously. Most of them had not looked at him the same way since they'd witnessed the takedown of the dragon. Bagman looked at him like Harry had stabbed his grandmother or something equally evil. Harry gave his most innocent smile.
"Alright, to the docks then. At the whistle, you have one hour to retrieve your treasure. Any final questions?"
The three contestants shook their heads.
"Alright. The scrying charms are all working?" Above the surface of the lake, an oily cloud spread across it. Shimmering, it focused into three sections, each with a fairly clear view of the lake, but from slightly different angles. Harry waved his hand over the rock and one of the sections blurred and was filled with a view of his hand. A magical video camera. Harry resisted the urge to start making rude gestures to it.
"Alright, line up contestants. On your marks - ready, set, go!" At the sharp blast of a cannon, Harry stuffed a hunk of gillyweed in his mouth. He coughed as the slimy texture assaulted his tongue. It tasted like an old, limp pickle - salty and mushy and ugh.
"Gah! Fuck you Neville, this is awful!" he gagged, his voice carrying through the scrying stone and projected across the stands. He heard the audience's laughter faintly in the back of his mind, too focused on the weird feeling of his skin morphing. Someone shoved him into the water and he gasped, struggling as his brain fought against the instinct to breathe normally.
After several moments spent panicking, he adjusted and swam around, getting used to the webbing of his fingers and feet.
Harry started swimming deeper into the lake.
He'd asked Professor Lupin about the history of the lake, and the man proceeded to accidentally spend an entire class period on the subject. Between the merpeople and the grindylows and the Giant Squid there were plenty of potential enemies to encounter.
But the most interesting and important revelation had been the reason it was called the Black Lake. An ancient, bloody battle - the result of a feud between the merpeople and a particularly aquaphobic ministry. The resulting massacre of the mermish population had stained the entire lake black with blood for many years. The undersea graveyard lay buried under layers of sand, the remains of the hundreds of slaughtered merpeople and the wizards who had slain them.
Harry searched outward with his magic, listening for the quiet, steady hum of death. He came to a large cave devoid of plant life and surrounded by carefully stacked rocks. It was pitch black inside, even with the gillyweed enhancing his vision. He peered into the darkness, wary at the thought of being eaten by something larger than him. He grabbed one of the smooth rocks and tossed it into the black pit.
It bounced around the interior, sharp pings as it hit rock. Nothing came out of the black to kill him so Harry swam in, feeling along the edge of the cavern to guide himself. There was no doubt he was confusing the shit out of everyone watching, but Harry was very glad it was so dark.
His hand slid against porcelain bone.
"Rise!" Harry said in Mermish. It came from his mouth in a trilling dolphin's cry. Talking underwater wasn't possible, even with the physical changes from the gillyweed. Mermish was powered by magic to ensure it was audible and was the best way to use spells if you knew the language. He'd tried to learn some Mermish-based spells but they couldn't find any in the library. The merpeople weren't considered real people, after all, and were not allowed wands. If they had decided to study magic regardless, then they had not printed that knowledge in any human books.
Luckily, not all magic needed silly things like wands and incantations. Harry had risen more beings from beyond the grave than he could count and could do so easily. It was only magic he was confident he could cast under the water. Which would have been fine had he not had the scrying stone pinned to his chest displaying potentially illegal actions to the whole school.
Again, Harry was very glad it was dark inside the cave.