The pirate and the demon (Billdip)

Chapter 1

Bill's POV

I swam up to the surface feeling very mischievous today, I wanted to cause at least a few deaths, I had been rusty and only expect to kill a good 30 people. It was the perfect day, storm clouds rolled in and a nearby ship was in view.
Not soon after thunder crashed and lighting struck, I swam under the ship and my eyes began to glow, my finger tip dazzled a bright yellow, I tapped the ship and cause a massive hole to be seen.
I swam back under and watched the magic happen, I was in shock when I saw a boy who looked to be only 18, he wore a bandana covering his forehead with a pine tree on it, telling everyone what to do, he seemed good at leading as well.
"Must be the captains son or something" I thought as my scaled ears drooped downwards.
But to my surprise there wasn't anyone on board who actually looked like his father, and old man yea, but probably his grandfather or great grandfather, definitely not his dad.
There was a girl on board who was also his age, she ran across the deck balancing herself when ever the boat tipped a little, she carried a small pocket knife and a bandana that covered her neck, it was pink and had a shooting star on it.
I wasn't paying much attention towards her I was more focused on the boy, why hasn't the ship crashed yet? I only saw a glimpse of it but I could've sworn he saw me, we made eye contact for what seemed like a whole minute.
Not soon after the ship was struck with lightning, the girl with the shooting star almost fell off the ship but the boy grabbed her and switched, he threw her body back and fell off instead.

There was something on his head... a constellation... it's glowing.

His body plopped into the ocean and immediately he lost consciousness.
I don't know why, but I was scared for him. I swam down as fast as possible and scooped him up hoping he was ok.
Why did I care? Why am I saving him?!
I swam up almost going above the water until I realized everyone was looking over board for him, I couldn't just pop my head up, I'm a rare siren after all, the only one of my kind. I swam away quickly so he could take air soon.
I found a rock that made like a wall and swam towards it, beside the rock was a cave, I swam underwater and entered the air pocket inside, this was my hiding spot.
I laid the boy down on the cold moist sand on the inside of the cave and prayed he would wake up soon.
I waited a minute and started to panic, I pounded on his chest and started to breathe heavily.
A cough was heard, then another.
The chocolate haired boy leaned up and coughed up all the water in his lungs
I hid behind a small rock but that didn't do much sense my scales glowed. He looked over and crawled slowly towards me.
"W-who are you?" He asked with the most soothing voice I've ever heard.
I wasn't scared I just hoped he didn't see me.
"I'm Bill." His eyes were fixed on my tail and I feel like his eyes glowed brighter then my scales.
"My eyes are up here you know..." I said wanting eye contact for some odd reason.
He looked at me and a wide smile was painted on his face.
"Were you the one who saved me?" He quickly questioned.
I nodded and my heart skipped a beat with that smile.
"Thank you so- m-much..." his eyes slowly began shutting and his hand held his head. I quickly rushed towards him and caught him keeping his head above the water I was in.
"Please relax, you were underwater for a while, you crew is fine, I refuse to let you go until you heal completely."
"Heh...thank you again..." he fell asleep in my arms and I carefully put him back on the sand.
"That's strange..." I thought, "he didn't say a word about me..." without hesitation, I switched from tail to legs, problem, the only problem is what I said earlier, I'm a special siren, a mixture with a demon to be exact.
A tiny pair of horns bulged from my hair.
I was actually only like that for a little bit before changing back to my normal form.
"Forgot I'm naked when I have legs...shit this will be a problem..." I sat in the water with my head resting on the sand. My fin ears perked up and I dove into the water, I looked outside and the ship was nowhere to be seen, the storm had gotten out of control and I was almost slammed back into the cave.
I swam towards the area where the ship was and I didn't see anything.
"Shit!" I yelled into the air.
"I heard something! It could be Dipper!" A unknown young voice shouted. I looked upwards and saw the girl on a small hill looking towards.
I dunked down and swam towards the side.
The whole crew was still there, I don't know where the boat went, but the crew was still there. Good.
I quickly swam back to the cave and poked my head through the water and saw the boy leaning over into the water meeting eye to eye.
His face was painted with worry and it was also a little to close to mine.
"W-where did you go? I woke up and you were gone..." I saw the fear and worry in his eyes.
"...what's your name?" He looked at me and without waiting.
"Dipper." There was an odd amount of silence until I broke it.
"How are you their captain?" He was filled with confusion.
"I mean like you get worried to easily, how can you manage to take care of a cre-" I was cut off by his calm voice.
"Although I've known them practically my whole life, I just met you, I don't want to lose you." His words stuck to me like glue and I grew quite red.
"Dipper?" I heard a older voice yell from the back of the cave.
His head jerked back and I ducked under water and behind a rock.
An old man burst through the other side of the cave with a lantern.
I don't know why he did but for some reason Dipper took off his bandanna and tied it to my wrist.
I starred amazing at the birthmark in his forehead and I was lost for words.
"T-thanks pine tree..." I slowly ducked behind the rock once more.
Right when I did the old voice grew louder and came into view.
It looked like a man in his 60's.
"Dipper your ok!" He grabbed pine tree and gave him a large hug.
"I'm fine gruncle ford, is the crew ok?" The man nodded and helped him out.
I looked at Dipper worried if I was ever going to see him again, dipper looked back at me with the same look.