You Do Need power plug adapter while traveling from Aruba to Cayman Islands.

Here is Why You Need An Adapter

The outlet and plug type used in Cayman Islands are A and B and in Aruba are A, B and F. This is how they look like.

Aruba

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

Type A

Type B

Type F

Cayman Islands

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

Type A

Type B