Ginnifer Goodwin

Ginnifer Goodwin is taking a trip underwater for a guest spot on SpongeBob SquarePants' upcoming special "Legends of Bikini Bottom."

In the clip, the Big Love actress, 32, lends her voice to a teenage mermaid who steals from others through Bikini Bottom's version of the Bermuda Triangle.

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"Welcome to Bikini Bottom Triangle" is one of four new stories included in the hourlong special. The first part of the special will debut on Facebook Thursday, Jan. 27, before it's TV premiere on Friday, Jan. 28 at 8/7c.

Watch the exclusive video:

Can you guess which mermaid Goodwin voices?