You Do Need power plug adapter while traveling from Saint Barthélemy to Costa Rica.

Here is Why You Need An Adapter

The outlet and plug type used in Costa Rica are A and B and in Saint Barthélemy are C and E. This is how they look like.

Saint Barthélemy

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

Type C

Type E

Costa Rica

In Costa Rica, outlets of type A and B are in use.

Type A

Type B