Sunken Vault

"It should be here," James commented, stopping the boat. Lupin's boat also stopped next to him.

They all looked out at the water. You couldn't see anything. The water was dark as if it were black. They could only hear the sound of the wind and their breaths.

"It's time to take the gillyweed," said James, pulling out four vials containing a green magical plant. The shape of the plant was not very appetizing, but they were to eat it.

He passed one jar to each person from his jar. Lupin did the same; from his purse, he withdrew four jars and handed one to each member of his boat.

"Bon appetit," Sirius said, and everyone at the same time ate the magical plant. Some have disgusted faces, and others hold their noses and swallow it instantly.

"Damn, it's disgusting," Sirius said, swallowing the seaweed. His smile had disappeared.

"That's what you get for tasting it," Snape commented. 

The gillyweed looked like a bunch of slimy gray-green rat tails; its taste was not good.

James felt his body begin to partially transform. It was a strange sensation, but it didn't bother him. When he became Animagus, it was a much more painful and savage process.

He saw membranes appear between the fingers of his hands and felt the same on his feet. The membranes were thin but tough, fish-like, and stretched gently when he wiggled his toes. It was as if his body was adapting to swim in water as naturally as walking on land.

Then he felt a twinge behind his ears. Instinctively, he brought a hand to his neck and noticed that gills had appeared. They burst through the skin, a series of slits that slowly expanded and contracted, processing oxygen from the water instead of air. As the gills formed.

Everyone experienced the same thing. They quickly took off their boots and robes and jumped into the water. The effect would last for an hour and a few minutes. It should be enough time to find the entrance to the vault. Just in case they had prepared another batch of gillyweed for each of them.

As they jumped into the water, none of them felt the penetrating cold they had felt just minutes before just by being in the boats. Their bodies instantly acclimatized to the low water temperature, as if an invisible protective layer had been spread over their skin, insulating them from the cold.

Even their eyes adapted, no longer needing to blink as often, and adapted to the aquatic environment, allowing them to see underwater, even though the light was dim and bluish.

As they breathed underwater, instead of drowning, they felt their gills process the water, sending fresh oxygen to their bodies. It was a strange but natural sensation.

Gillyweed is the best choice for scuba diving. You can move with the speed of a fish, breathe underwater, and see with better clarity than before underwater.

The only disadvantage was that they couldn't talk because of the water, but they had prepared themselves. They all knew what to do. As they submerged, they formed themselves in such a way that they could defend themselves from possible hostile creatures. 

They began to descend further and further.

Algae floated as ghostly curtains and shadows of large creatures moved in the gloom, but the gillyweed allowed them to swim with the grace and speed of fish, keeping them alert and ready for any eventuality.

Amid the underwater gloom, James spotted four small, shadowy figures gliding swiftly toward them. Focusing his gaze, he recognized them almost immediately: Grindylows. 

Just as he had read, they were small, sickly green creatures with sharp horns adorning their heads. Their faces, grotesque and misshapen, showed mouths filled with dozens of pointed teeth, and their long, slender fingers twisted with sinister agility. Tentacles emerged from their undersides, waving erratically as they rapidly approached the group.

The creatures emitted high-pitched roars of delight as they sensed the presence of humans, swinging their long arms with predatory impatience. It was evident that it had been a long time since they had come across such appetizing prey in the lake.

Realizing the impending danger, Sirius, Lupin, Snape, and Regulus quickly unsheathed their wands, which they had kept in their belts during the descent. The membranes that now covered their fingers due to the gills made holding the wands more difficult, but not impossible. They had trained with fake membranes, and although their movements were clumsier, they could perform a simple spell like Relashio with no problem, even non-verbally (this is thanks to the training they did with James in the Room of Requirement).

Jets of boiling water spurted out of the four wands, which spurted swiftly towards the Grindylows. The creatures, taken by surprise, were hit squarely, grunting in pain as their bodies writhed under the searing heat. But far from deterring them, the attack only enraged them further. With renewed rage, they charged toward the group with even greater ferocity.

Without losing his cool, James watched the creatures' onslaught with an icy expression. As one of the Grindylows lunged toward him, he extended his hand with lethal precision, concentrating his telekinetic energy. Suddenly, the Grindylow was suspended in the water, immobilized amid its attack. The creature struggled, its eyes filled with hatred and fear, but it could not break free.

With a swift movement, James closed his hand into a fist, and the Grindylow's neck twisted with a dry snap. The creature let out a final groan before its limp body slowly fell to the bottom of the lake.

The other three creatures, which had been poised to attack, came to a screeching halt. Their eyes once filled with fury, now showed wariness and fear toward James.

Their beast instincts warned them of the deadly danger they were in.

Without hesitation, the Grindylows turned and fled in terror, leaving a trail of bubbles in their haste to escape.

James didn't bother to chase after the ugly fleeing creatures. He would not waste his time. He continued his descent. Not noticing the looks everyone was giving him.

The descent after that little incident went smoothly. It took them about fifteen minutes to reach the depth indicated on the scroll. 

What they had not noticed was that several Selkies and Kelpies had observed their group but decided not to get in their way. The reason? They saw the fate of the Grindylow, and their instincts told them that it was better to stay away from this peculiar group. Especially from the boy who led the group and killed the Grindylow.

At the right depth, they began their search. It did not take them long to find what they were looking for. Although they did not know what exactly they were looking for, it was obvious that it would be some half-hidden structure in which there was a door, and indeed it was.

It was a large circular door embedded in a rocky wall covered with algae and aquatic moss. The door, like the previous ones, was decorated with engravings of ancient runes.

Right in the center was a small square sticking out. James cautiously approached it. He reached out his hand and pressed the square button. For a moment, nothing happened, but then the door gave off a soft glow, and the runs began to glow a deep blue. With a slight shudder, the door slowly opened, revealing a dark passage that descended further into the bowels of the cave.

Without hesitation, they began to swim through the passage. As they progressed, they noticed that the tunnel began to slope upward, signaling that they were approaching the water's exit. The water became shallower, and, finally, they began to feel the ground beneath their feet.

They emerged into a large subway chamber. They emerged from the water, and James quickly pulled out some potions that returned them to their human forms. Canceling the effect of the gillyweed a few minutes left.

"That was faster than I thought," commented Lupin, glad to be a human again and breathing normally.

"Yes, and a lot easier," nodded James. They only encountered a few Grindylows and nothing else. The trip was uneventful.

James cast a spell to dry his clothes. The others did the same and then surveyed the room in front of their eyes.

There was nothing of importance in this room. Only a stone path led into the darkness. Without wasting any more time, they started to head towards this path that should lead them to the great treasures of Dai Ryusaki.