The time of death is a clear one.
The heart stops, The lungs cease expanding, and the electricity inside of the brain slowly declines into nothing. This electricity fuels a person, makes their body move, and lets them be a human being.
The cold water on the boy's face is sweet and gentle, despite the salt that stung his eyes. He could only feel the warmth of the sun above him, feel himself drift beneath the waves, and the ice-cold scattering throughout his body.
He doesn't want to die.
He feels the aching cold spreading through his body from the bloody bite on his shoulder and he simply lets go.
As he closes his eyes, the dying teenager briefly sees the image of a girl reaching out toward him and the boy holding her inside of their boat. He sees them and he closes eyes, letting the cold spread through him and take him away. Tears trickle down his cheeks only to mix with the salt of the ocean.
Sora doesn't want to die, but he has no choice but to let go.