You Do Need power plug adapter while traveling from Marshall Islands to Saint Martin.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Martin are C and E and in Marshall Islands are A and B. This is how they look like.

Marshall Islands

In Marshall Islands, outlets of type A and B are in use.

Type A

Type B

Saint Martin

In Saint Martin, outlets of type C and E are in use.

Type C

Type E