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The Moon Pool is a special, supernatural pool with the power to transform normal people into merpeople when the Full Moon passes over the top of the cave (in Mako Island) and passes in the front of the cave (Sea Caves of Ireland).

These places were formed on Earth after collisions with a comet containing Moon Rocks and Crystal that generate special powers corresponding to the Moon (revealed in "A Magnetic Attraction"). The underwater cave that leads to Moon Pool is roughly 50 feet deep.

There are currently two known Moon Pools: one on Mako Island in Australia and another in a Sea Caves of Ireland in Ireland.


In the early seventeenth century, a mermaid named Eva transformed in a Moon Pool in an Sea Caves of Ireland. During that time, a comet was about to hit the earth and she used her powers to form the original Tower of Light to change its course. In the late 90s, a young girl named Bella was transformed in the same place when she was nine years old. The first known people to become mermaids in Australia were Gracie Watsford, Louise Chatham and Julia Dove, all of whom were transformed in the 50s and were given special powers.

In the early 2000s, Cleo Sertori, Emma Gilbert and Rikki Chadwick were transformed into mermaids in the Moon Pool.Charlotte Watsford, Gracie's granddaughter also became a mermaid in the same place. However, as she fell into the Moon Pool during the most recent planetary alignment, her powers were taken away forever.

The Moon Pool is destroyed in the Season 3 by Ryan, Sophie and Zane, and becomes a communal pool. The Full Moon gets only reflected in the water, not releasing magic because Ryan blew up and destroyed the Moon Pool's cave in search of Moon Rocks.

Despite its destruction in Season 3, the Moon Pool somehow becomes active once again in Mako: Island of Secretswhere a young boy named Zac Blakely becomes a merman when he falls into it (although it is later revealed that he was a natural born merman, and his fall into the Moon Pool merley broke a spell that prevented him from growing a tail). Later, his girlfriend Evie McLaren would accidently become a mermaid as well. In Mako: Island of Secrets, the Moon Pool is completely different in appearance than how it appeared in H2O; the original entrance from land has disappeared, instead it was relocated to another side of the cave. According to Rikki in Mako: Island of Secrets , the Moon Pools new appearance has been around since she and the others left, implying that they are somehow responsible for its remodeling.


When the moon is full, it passes over the volcano top of Mako Island or in front of the Sea Caves of Ireland and activates the magic in the water. During this time, any human that stays in the Moon Pool will be transformed into a mermaid/merman and given special powers over water. When the Comet Eva is about to collide with Earth, the Moon Pool creates a Water Tentacle to warn the mermaids about the comet. Its magic is active only on a Full Moon.


The Moon Pool's magic is active only during a full moon. During this time, any human who jumps into the pool when the moon passes over, will be turned into a mermaid or merman, and given special individual powers. The Moon and the Pool generate different magnetism and effects depending on the moon's phases and the planetary alignments. When nearing collision with a comet, the pool's temperature will rise in preparation for it.

Special Planetary Alignment

During a rare planetary alignment, the moon will increase the powers of a mermaid if they are in the Moon Pool during the alignment.

  • Hydrokinesis - (Aerokinesis)
  • Hydro-Cryokinesis - (Cryokinesis)
  • Hydro-Thermokinesis - (Pyrokinesis/Electrokinesis)

If one mermaid has all three powers, they will be upgraded in the same way.

The Moon of Fifty Years

At every fifty years another planetary alignment takes place. If a mermaid is in the Moon Pool during this alignment, they will lose all of their mermaid powers, returning to being Human.

Lunar Eclipse

During the Lunar Eclipse, the mermaid who is in the Moon Pool, will lose their powers for 12 hours only. After 12 hours, their tails returned, along with their powers.

These effects apply only to human-turned-merpeople, because they are merpeople via the Full Moon and the Moon Pool, and subsequently, the Full Moon reacts and can increase or remove their powers and mer-form according their alignments. 


  • There are two known Moon Pools in the world, one on Mako Island, in Australia and the other in the Sea Caves of Ireland. There may be more Moon Pools, but these two are the only ones known.
  • When the Moon Pool is active, technology does not work. Probably due to magic.
  • Its magic is active only during the Full Moon.
  • Both the Crystals and Moon Rings store Moonlight and can be used to simulate a Full Moon.
  • These places were formed after a collision with a comet, a piece forming Mako Island, and another one of the pieces formed the Sea Caves of Ireland.
  • A potion of full moon magic amplified by fifty which causes magic-made merpeople to lose their mer-form, has to be used in the Moon Pool during the Full Moon.
  • In Mako: Island of Secrets, it is revealed that if a normal human touches Moon Pool water while outside of the pool, it gives them water-based powers that gradually loses balance. However, this only applies in Mako Mermaids.


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