ONE boy is dead after crashing an unregistered car near Griffith while another is unhurt after his car ended up in a swimming pool in Sydney.

In the first incident, a 15-year-old boy crashed while driving an unregistered car on a private property in Kooba, near Griffith at about 7.30pm last night.

Residents on the property heard a smash and found the vehicle on its side in a paddock, police said.

The boy died at the scene.

In the second incident a P-plater ended up in a backyard swimming pool after losing control of his car in Kearns, near Macquarie Fields.

The 17-year-old driver told investigators he mounted the kerb after losing concentration, before driving through a metal fence and into an in-ground pool, police said.

No one was injured.

Police expect to lay charges against the 17-year-old, including negligent driving.

Inquiries are continuing into both incidents.