You Do Need power plug adapter while traveling from Sint Maarten to Cook Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cook Islands is I and in Sint Maarten are A and B. This is how they look like.

Sint Maarten

In Sint Maarten, outlets of type A and B are in use.

Type A

Type B

Cook Islands

In Cook Islands, outlets of type I are in use.

Type I