The Silkie

The Silkie -- A living spaceship, impervious to heat and cold, virtually indestructible and capable of travelling at supersonic speeds.
The Silkie -- Similar to a human being, but not the same. Highly intelligent.
The Silkie -- Able to live under the oceans with the ease of a dolphin and the speed of a shark.
The Silkie -- A modern angel or a computerized demon?
The Silkie -- A friend of Earth, or a pitiless, alien destroyer?