Homecoming

Rikki noted that she missed her friends badly, which confused her as she knew they would have to go their separate ways as adults and not see each other much. To her surprise, the natural mermaids explained that the metamorphosis didn't just give her the biology and magic of being a mermaid; it also imprinted on her the need to be in a Pod. Which explains why the girls always got together outside of protecting or exploring their secret; they were just natural drawn to each other to form a Pod.

Rikki (Cariba Heine) says that the Moon Pool hasn't changed since she last saw it. However, the Moon Pool set used for Mako Mermaids (2013) looks vastly different from the set used in H2O: Just Add Water (2006).

Though seeing as the Mako Pod wasn't guarding the island moon pool the day she, Cleo and Emma fell in and became mermaids, it's likely Mako Mermaids takes place in a similar but different universes than the original H20. Explaining the discrepancies.

References H2O: Just Add Water (2006)