Why do you assume it's going to fall in the ocean?
They might target Sidney (see their recent threats) and a misfire might get that rocket to land in Delhi , or Kuala Lumpur.
Or they might hit China, that would be something like a karmapocalypse.
First of all, let's rule out Sydney. The North Korean missiles are not capable of reaching the Australian continent. And secondly, North Korea will never ever launch a missile over the Chinese air space. China is one of the last remaining allies of the DPRK, and they will never do something which can harm that relationship.