I had this thought. Rita tells two of the girls that if Zac takes the Trident into the Moon Pool on the full moon he will destroy the Moon Pool?. In the trailer we see Zac in the moon pool with the trident and lightening striking into the pool and hitting the trident. So what if this ide happens?.
What if Zac destroys the moon pool we know in Mako Mermaids. Some how this is the 1st moon pool design and someone is able to rebuild the moon pool but it looks like the design we come to know in H2O Just Add Water?.