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

Here is Why You Need An Adapter

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

Costa Rica

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

Type A

Type B

Tahiti

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

Type C

Type E