You Do Need power plug adapter while traveling from Saint Vincent and the Grenadines to Swaziland.

Here is Why You Need An Adapter

The outlet and plug type used in Swaziland is M and in Saint Vincent and the Grenadines are A, B and G. This is how they look like.

Saint Vincent and the Grenadines

In Saint Vincent and the Grenadines, outlets of type A, B and G are in use.

Type A

Type B

Type G

Swaziland

In Swaziland, outlets of type M are in use.

Type M