Moon over water

The Moon

Full moon.

The Moon is Earth's primary satellite and, in mermaid shows, is often given magical associations.


The moon, combined with a special body of water or magical object, often causes the initial mermaid transformation, as in H2O.

Moon StrikingEdit

Moonlight tends to have a strange effect on mermaids. They become "moonstruck," acting wild, seductive, flippant or otherwise out-of-character, and sometimes gain unusual powers. Again, this primarily comes from H2O (and thus the full moon), though there is a mythological link between the moon and temporary insanity.

Lilly and Eclipse gain waterless tails from moonrise-to-set, but their minds remain unaltered.
Emma Seeing Moon Reflection

Emma, from 'H2O: Just Add Water', catching sight of the full moon's reflection and becoming instantly entranced with its power.

Bella actually dealt with this problem: when she and her sister got to choose new powers, one of hers was a "moon shield" that would protect them from lunar influence.

Along with moonstriking, the full moon throws Holly and Claire's powers out of whack (such as Holly demonstrating cryokinesis or Claire pyrokinesis without having these powers before) as aftereffects a few days later.

For Hailey, Brooklyn and Merlena, moonstriking was rather ambiguous: the obvious reaction was unnaturally white faces for the duration of the night, but the morning after, the girls used their powers for the first time. Whether this was coincidental or caused by the moon is unclear.



The full moon is very popular for initial transformations, moonstriking and upgrades, again following H2O. This can be seen in shows like Another Mermaid Story or The Mystic Tails (in which the moon actually resurrected Kylie as it changed her). It can also grant powers, even though the mermaid in question (Avery) didn't remember it happening. The full moon also has many effects on mermaids and mer-men in the Netflix H2O spin-off Mako Mermaids.


The 3 Tails and Mermaid Secrets departed from formula slightly by using a half-moon for their mermaid transformations, and The Tail of 2 Mermaids used it for moonstriking. Given that a half-moon can be out during the day, when these scenes are usually filmed, this seems the more practical option. Most shows do not distinguish between the waxing and waning half-moons, though.



The crescent moon moonstruck Jane, throwing her powers out of whack.


Blue MoonsEdit

A blue moon is when a full moon arrives less than one calendar month (28 days) after the previous one. These typically occur every three years or 33 months. On mermaid shows it can sometimes be the moon actually turning blue, but this is a rare occurrence--magic aside, it can be caused by particles in the air, like ash after a volcanic eruption or forest fire.

Lunar eclipse low


Eclipses and other unique events (real or otherwise) also have an effect on mermaids. Sometimes they cause the transformation, or following H2O, remove a mermaid's powers, temporarily or permanently, as well as upgrade them. In the case of Kristie, a wish combined with the eclipse transformed her into a mermaid. Likewise, Trinity and Brook were turned when they entered Secret Scale Lake in order to view a lunar eclipse (or as they called it, Blood Moon) better.


There are a number of gods and goddesses associated with the moon, who are occasionally mentioned or invoked in mermaid fiction. Some of the more well-known ones include Artemis and Selene from Greek myth, and their counterparts Diana and Luna in the Roman version.

In one instance, the moon itself was a sentient being, one that communicated to Claire either directly or through an agent, Kiki. She was also the one who chose Claire to become a mermaid. During the full moon when Claire was moonstruck, the moon also lost control of herself.


Each full moon of the month has its own name. Here are some common ones in North America:

  • January -- Moon after Yule, Wolf Moon, Old Moon
  • February -- Snow Moon, Hunger Moon
  • March -- Sap Moon, Worm Moon, Crow Moon, Crust Moon, Lenten Moon
  • April -- Grass Moon, Pink Moon, Egg Moon, Fish Moon
  • May -- Planting Moon, Flower Moon, Corn Planting Moon, Milk Moon
  • June -- Honey Moon, Strawberry Moon, Rose Moon
  • July -- Thunder Moon, Buck Moon, Hay Moon
  • August -- Grain Moon, Sturgeon Moon, Green Corn Moon
  • September -- Fruit Moon, Harvest Moon, Corn Moon
  • October -- Hunter's Moon, Harvest Moon, Blood Moon, Sanguine Moon
  • November -- Frosty Moon, Beaver Moon
  • December -- Moon before Yule, Cold Moon, Long Nights Moon

Super Moon Edit

supermoon is a full moon or a new moon that approximately coincides with the closest distance that the Moon reaches to Earth in its elliptic orbit, resulting in a larger-than-usual apparent size of the lunar disk as seen from Earth. The technical name is the perigee syzygy of the Earth–Moon–Sun system. The term supermoon is not astronomical, but originated in modern astrology. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions