I'm not the best audience for tv series because I get bored very easily and I drop them after two episodes but I have to admit that's not happening to me with Siren, I'm currently watching the 2nd season and even though I think the first season holds you in a way it's so hard to abandon the show and you're just like "Omg, one episode more and then, I go to sleep"...the show lost strength by the second season, I'm in the 11th episode and it's way harder to continue, I don't feel attached like I did in the first season, anyways, I strongly think this TV show deserves the opportunity and it's a must watch for anyone into fantasy/drama.
UPDATE: I already finished season 3 and I must say this was the best cliffhanger ever, RENEW SIREN PLEASE, IT JUST GETS BETTER, I CAN'T STOP