I first watched this animation on Youtube several years ago; 4-5 is my best guess.
What I remember:
- The girl wore yellow and had either blue hair or eyes; or both
- The boy was an assailant trying to kill the girl
- On a ship, later an island, and then a ship again
- Vibrant colors
- Something really sad. I cried hysterically, I don't remember why. This is also the main reason why I am trying to find this animation
- I remember the boy could shift into a shark
- The girl was somewhere between 3-6 years old, and the boy was more teenager
Is there an animation that fits this description?
Edit: I think the boy's name was some color. I don't remember which color though.