Over the weekend at New York Comic-Con, Freeform announced that the new original drama “Siren” will premiere on March 29th with a special two-hour episode. The network is calling the day “International Mermaid Day,” highlighting the supernatural wonder that is at the very center of the “Siren” storyline.

Also announced during this weekend’s panel was the casting of Aylya Marzoff (“Grandfathered”) and Sedale Threatt Jr. (“Hap and Leonard”) who will both join the cast in recurring roles. Marzoff will portray Katrina, an alpha leader of the mermaid colony, while Threatt Jr. will portray Levi, a warrior merman with an imposing presence.

Freeform’s new series takes place in the coastal town of Bristol Cove, known for its legend of once being home to mermaids. The town is turned upside down when a mysterious girl (Eline Powell) appears and begins wreaking havoc upon the small fishing town. Using their resources, marine biologists Ben (Alex Roe) and Maddie (Fola Evans-Akingbola) must work together to find out who (or what) drove this primal hunter of the deep sea to land, and to find out if there are more of her kind out there.

“Siren” is based on a story by Eric Wald and Dean White who both serve as executive producers. Emily Whitesell (“Finding Carter”) serves as showrunner and executive producer. Brad Luff, Nate Hopper and RD Robb also serve as executive producers.

Freeform also confirmed the premiere dates for “Shadowhunters” and “Beyond,” two series that have quickly grown a dedicated audience. You can find those premiere dates here, along with more information on Freeform’s upcoming Fall/Winter lineup. When “Pretty Little Liars” ended, it was unclear which of the existing series would float to the top. Instead, several series have become mega-hits on both social-media and weekly television and digital ratings. Bella Thorne’s “Famous in Love” already has another season on the way, and the popular series “The Bold Type” already has two seasons on the way. Even with these series pulling in audiences on a weekly basis, Freeform is also launching two new Marvel series over the next few months. “Marvel’s Cloak & Dagger” and “Marvel’s New Warriors” are expected to launch to terrific ratings on the network, making Freeform the place to be for millennial advertisers.