You Do Need power plug adapter while traveling from Namibia to Cocos (Keeling) Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cocos (Keeling) Islands is I and in Namibia are D and M. This is how they look like.

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M

Cocos (Keeling) Islands

In Cocos (Keeling) Islands, outlets of type I are in use.

Type I