As you can see on the summary, I have come to see this episode as a very good chance to be creative, that went down the gutter. I also consider this episode as the beggining of the decadence of what I look to as my personal favorite show.
The mermaids are something that has always amazed me (probably because I have had a crush on The Little Mermaid's Ariel since the moment I saw that movie for the first time), but that, personally dissapointing for me, has never been portrayed in a way that takes these beings out of their own clichéd personality, always portraying them as silly, weak, helpless and oftenly not to far away from being inmoral and innapropiate.
Charmed, was not an exception in this particular flaw.
Mylie was a woman who was willing to give up her inmortality on behalf of her love, a human man who (according to her own fears) wouldn't have understood her nature, and the reason of her white-lying.
Although Mylie's story was a badly performed blatant rip-off of my Disney favorite mentioned above, I still didn't hate it. The sea's hag was a very good demon-ish being, and Necron was a little intimidating (which is rare in the demons of Charmed).
Apart from the main plot of this episode, the Phoebe-Cole sub-plot also reestarts. Again. And guess what? It's just as interesting as it was when it began. Meaning, that it is BORING. This storyline should have been vanquished for eternity (along with Cole) in "Be Careful What You Wish For", but that paticular wish, was not granted to the sane charmed viewers, making the first half of one of the worst seasons of Charmed, an absolute dissapointment. At least, the demise of the storyline in "Centennial Charmed" was a very good way from the wqriters to redeem themselves of a horribly written and developed storyline.
Overall, this episode is very average, abd not very clever, even when it had the potential to be a good installment.
I am very soft-handed when it comes to rating episodes (specially Charmed episodes), so, despite of being dissapointing, I give it 7.5 out of 10.