You Do Need power plug adapter while traveling from Northern Ireland to Sint Maarten.

Here is Why You Need An Adapter

The outlet and plug type used in Sint Maarten are A and B and in Northern Ireland is G. This is how they look like.

Northern Ireland

In Northern Ireland, outlets of type G are in use.

Type G

Sint Maarten

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

Type A

Type B