WATCH: Siren cast takes us behind the scenes of this week's underwater mermaid fight

It would be a mistake to mess with the mermaids on Siren. The Freeform original series made that point very clear in this week’s episode, which featured a vicious mermaid fight between Ryn (Eline Powell) and Katrina (Aylya Marzolf). Unlike previous mermaid sequences, this battle was in very tight quarters and in full view of both the audience and the human characters.

SYFY WIRE’s latest behind-the-scenes look at Siren Season 2 focuses on that mermaid fight, and Powell was very proud of what she and Marzolf accomplished there.

“There’s a lot going on in that scene,” said Powell. “It’s all us except for when Ryn and Katrina fall in. That fall was amazing stunt people. Then the actual fight, once we’ve turned mermaid, is all us.”

“It was quite something, especially because they’ve done really amazing training about the breath hold,” added Siren co-star Fola Evans-Akingbola. “They were doing their free diving and holding their breath, then going under and doing the fighting. They are both so balletic under the water.”

Powell also expanded upon playing the scene with Marzolf, and her appreciation for her underwater skills. She also revealed that the two mermaids had a surprising inspiration for their battle movements, but you’ll have to watch the entire video to learn what it was!

Siren airs Thursday nights at 8 p.m. ET on Freeform.