1-This looks like "Rod Serling presents Splash!"
Which is pretty bad, considering that we already HAVE a "Splash" rip-off ("Aquamarine", ever heard of that?).
2-When I saw the teaser in theaters, it got advertised as a cuddly, warm, family friendly fairy tale, kinda like "Shrek2 on water.
But now Shymalan realized no one will ever watch any of his movies if he suddenly switched genres (look what happened with Wes Craven and "Music of the Heart"), so he added the evil water creatures and made it into a horror movie.
I would actually prefer if he stuck to one genre instead of having movie-genre-schizophrenia
3-Why do the water creatures look human?
That worked in the Aquaman comics, but it doesn't work here.
Wouldn't it make more sense if the water people looked completely different from us, and when they arise to the surface they have to hide them or people will panic, ala "E.T."?
4-I'm not the least bit suprised about this being a "Twilight Zone" episode.
Shyamalan is not a terribly original guy, and most of his movies tend to rip off the feeling and themesof "The Twilight Zone".