Still no answers, but at least the show is starting to address the questions.
While it wasn't nearly as big of a blow-up as I expected, the plot has finally begun to move. I really liked how the change in tone flowed naturally from the scenes we've come to expect from the show (fishing!) into something a bit more dark and crazy (Haru loosing his mind). Something was bound to happen though, otherwise all the sudden backstory about Akemi and how fisherman never go there would've been wasted.
I admit, I'm a little disappointed that the artificial reef wasn't brought up until now, since it played such a big role in this episode. It played nicely into the dragon myth though, so I'm willing to let that slide. The additional details on the dragon myth--specifically, people being spirited away--is pretty interesting within the context of the episode as well. For the most part, this episode seems to follow the lines of a common mythological story; a god or gods tell humans not to do a specific thing, the humans do it anyway, and the gods get mad. At least, that was my understanding of what happened in this episode.
What threw me off in this episode was Haru. His brand of weirdness has become standard, and with all the hints that had been given up until this episode, I was convinced that he was a fish. But this episode makes it clear that there's something more going on here, even if that "something" is anyone's guess. My current theory is that the dragon/ocean spirit/whatever the hell lives in/near Akemi is a similar being to Haru and his sister, but a much more powerful one.
I'm also 99.9% sure that Haru was possessed in that scene, since he seemed to be acting like a broken record more than anything else ("Sakana ningen uchuujin!") but when he pulls the water gun on Akira, his hand shakes and hesitates while he looks at it like it's not a part of him. That seemed like the "real" Haru to me, since he was willing to throw the thing in a ocean not too long ago. Why he hesitated with Akira (who still hasn't earned his "friend" status yet) is still a little confusing to me with this theory.
Anyway, it seems like we're getting close to how all these threads connect. The story of the fishermen disappearing near Akemi and the "spirited away" part of the myth are clearly related. But how did it get to be that way? Was the dragon/god/whatever mad that something artificial had entered its domain? What exactly do Haru and his sister want to do about it? What does the the Duck (or DA-KU, I'm not really sure) Organization have to do with all this? I could keep going, but you get the idea. There are still a lot of things left to be addressed for this show's second half.
The end of the episode also seems to hint that we'll get a straight answer on what Haru really is and why he came to Enoshima next time. Of course, that could also be a complete red herring... In any case, now that things have begun to move, I expect that we'll get pretty heavy plot revelations from here on out.
Images from Crunchyroll.com.