This is loosely inspired by the Mako Mermaids/H2O universe. This is a multi-chaptered AU fic, very different from the other fic I have planned for them, which is a one-shot and in a opposite universe, and I truly hope you enjoy them both *wink wink* maybe tell me which one you like better and what you like to see next *wink wink*.

Also I just got accepted at a uni program of teaching so my weeks will be hectic, and updates really slow.

With that being said, please enjoy.

Tom didn't know what could possibly happen when he entered that cave on that summer, full moon night. All he knew was that it was a very, very weird cave. And that this wasn't supposed to happen.

It all started when he went camping on the Downton Isle with his friend Matthew. It wasn't his ideal way to spend the weekend but still it was better than staying at home and working all summer.

Matthew and Tom knew each other ever since they were babies, his mother Isobel was a midwives along with Tom's mother.

He woke up in the middle of the night and started walking, unable to sleep any more. It was dark and there was something about the isle that always fascinated and questioned him.

He barely had time to process where he was stepping at when he fell into a hole. His ankle hurt and he knew he had to find a way out of there. But he couldn't possibly go up from the hole he fell, he had to follow the cave and see where he would end up at.

It was really tight, and he couldn't possibly go up in the same way he got in, and He knew it was useless to scream. Yet the sound of running water gave him an idea.

He followed the sweet sound of water until he found d a small pool. It gave him a way out and also a location. The downton Isle had an old and highly inactivated volcano, and a small pond must have formed there throughout the years. It was truly a beautiful sight. If only he had a camera to capture this image.

The moon was fully showing on the opening on the top of the cave and it was truly the best sight Tom had ever seen.

Well, he would have to come back here.

But first he had to go out. He jumped onto the small pool and had no time to think about swimming away when the water started mysteriously and oddly bubbling. Almost as if it was boiling, only the water wasn't hot.

The whole thing lasted for only a few seconds and when it stopped Tom didn't even dared to look, all he did was swim away, and try to find his way back to his camping area.

Little did he know that three pairs of eyes watched him swimming away, and they weren't very happy to find about where he was. One of them tough, looked at him not with despair as the other two but instead with wonder. Two tried to chasse after him but the younger one stopped them both.

And now, on the following morning Tom woke his best friend and told him it was time to leave.

"Are you serious?" Matthew asked, clearly annoyed that he would have to leave and also that he was woken by Tom. "You told me we would spend the weekend here! Also where were you?"

"I got lost." Tom lied quickly. He knew his friend would never believe in him. A bubbling pool inside a cave? Heck, not even Tom believes in what he saw.

When the two young men got inside the boat and left the Isle slowly the same three creatures that watched Tom swim away that night looked at boat. One of them started to follow, but the other two held her back.

"Mary!" The youngest of the three spoke. "You can't go in there!"

"Yes I can." She spoke, being the older one; Mary knew her sisters couldn't argue with her, besides this could ruin their entire family.

"We don't know what happened to the boy, it may be nothing, and he may not even have seen anything." The middle one spoke. Edith knew clearly something must have happened; she just didn't want to think about it. And besides Edith won't allow Mary to have her way again.

"We need to see what happened, but we cannot hurt the boy, or let our family know about this. It was our job to protect the cave; it is our job to work it out." Said the youngest, Sybil. She had no idea of what could possibly happen if a human entered the moon cave and the water on a full moon. The full moon in their force, their strength, if a human walks inside it they are ruined.

Maybe nothing would happen or maybe everything would happen and change the world as she knew. But right now all Sybil knows is that she needs to find that young man and find out exactly what happened.

"And is your suggestion, Sybil?" Mary spoke, angry and clearly demanding an answer right away "We let it be and go on with our lives, knowing our secret may just be exposed?"

"I saw we follow him." Sybil said and could hear Mary whisper an 'i told you so' to Edith, but before the oldest could brag any further Sybil continued. "But we will not reveal ourselves, or do anything. We will just see if he became something or worse if he will die."

"Die?" Edith questioned, she truly didn't think that entering the moon pod would kill that boy.

"Well, as far as I know, no human has ever entered the moon pod before." Sybil answered. No, she did not want the boy's death. She really doesn't want him to die; she just wants to know what has happened to him and how they can fix it.

With a sigh Mary agreed and the three started swimming and following the boat carefully.