The show is definitely watchable and enjoyable. This being because of the plot being mermaids and sirens. Unfortunately the writers do a terrible job of being consistent and reasonable, meaning you have no choice but to ignore many mistakes or you will hate this show.
SPOILERS BELOW
from just season one there are many mistakes and stupid writing/filming errors. On example is when the siren just casually phases through her restraints and attacks everyone. The scene made so little sense it infuriated me. And it's literally such a simple fix, all the show had to do was show her cutting trhough them or something. Stuff like this piles up and just seems like laziness on the shows part. There are also issues with the mermaids strength. There are scense where mermaids are tossing people around like they have super strength and scenes where humans are easily blocking there attacks or even pushing them over ect. Just doesn't make sense and again infuriating. I'm only on season 1 and really don't think I'll watch season 2 unless this season finale cliff hanger blows my mind.