You Do Need power plug adapter while traveling from Saint Helena to Bahamas.

Here is Why You Need An Adapter

The outlet and plug type used in Bahamas are A and B and in Saint Helena is G. This is how they look like.

Saint Helena

In Saint Helena, outlets of type G are in use.

Type G

Bahamas

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

Type A

Type B