“Mako Mermaids” may look like the CW teen drama that never was, but it could give Hollywood more Netflix nervosa when it starts Friday on the streaming service.

A spin-off of an Australian show called “H2O: Just Add Water,” the teens-as-mermaids series is the latest in Netflix’s inaugural year of original programs, preceded by Emmy-nominated fare that is already shaking up older legacy networks. The Netflix lineup includes fare like the political drama “House of Cards” and the revived version of “Arrested Development.”

It’s a safe bet that critics won’t go quite as wild for “Mermaids,” given that its technical achievements look fairly budget-constrained and the scripts seem to depend heavily on fish jokes.

PHOTOS: Cable versus broadcast ratings


But none of that may matter if the show connects with its target audience. If teens watch on their laptops or tablets, that could mean big trouble for everyone from CW to MTV to Nickelodeon, whose businesses are built on guessing what American youth wants. Already, Netflix has made a big play for the HBO/Showtime audience of educated elites with “Cards” and the new dark comedy “Orange Is the New Black.” Teens may be next on the hit list.

For now, rivals will just have to guess how popular “Mermaids” will be. Netflix has refused to release any audience data and isn’t measured by Nielsen. During a Google Hangout on Monday, a Netlfix executive said its original series were drawing “TV-size audience numbers” -- whatever that means.

Check out the “Mako Mermaids” trailer above, and let us know what you think in the comments.

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Twitter: @scottcollinsLAT