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.
North Korea could launch missile soon South Korea and Japan. Theoretically, in order to launch a missile at Australia, Kim does not need to cross the airspace of China, but they have no such long-range missiles. In addition, after the deployment of the ABM systems on the territory of South Korea, no rocket will not be able to pass undetected.