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

Here is Why You Need An Adapter

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

Saint Martin

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

Type C

Type E

British Virgin Islands

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

Type A

Type B