Poseidon
Poseidon is the middle child of Cronus and Rhea. After Cronus’ death, his brother, Zeus, distributes the world among himself, Hades and Poseidon. Poseidon tries to prove he’s as powerful as his brothers, but he makes a terrible mistake, creating a monster out of a girl called Medusa, a threat to mortals and immortals alike. In his despair, he gives up his undersea kingdom and disappears in a faraway location, Calypso’s island. Soon though, he will meet a group of young sea gods who will make him realize his decision might not be the solution to his mistakes. Medusa will threaten the ones he loves and he will finally have to be the hero he always wanted to become.

Zeus
Zeus is the youngest son of Cronus and Rhea. He defeated his tyrant father Cronus and he gained control of the world. Since that day, he thinks he is the best thing that ever happened to the universe. Cocky and selfish, he finds it very amusing to harass Poseidon and make him feel less than what he actually is. His brother, Hades, always follows him and flatters him. Zeus is the one who makes Poseidon give up his kingdom and flee.

Hades
Hades is Cronus and Rhea’s eldest son. He was given the kingdom of the Underworld to rule. At first, he’s not very excited, but afterward, he gets to enjoy his new realm. He doesn’t have much of a personality of his own. He pretty much follows Zeus in whatever he does, including harassing Poseidon.

Calypso
Calypso is Poseidon’s cousin and the owner of a private island and a business called “Calypso’s Spa and Resort”. Calypso has taken a sacred oath to always accommodate those in need. Sadly, a god or immortal can also stay as much as they want on her island, making her their eternal servant. Her cousin, the sea god Proteus, has taken advantage of her hospitality and when Poseidon arrives on her island, Proteus suggests that he does the same; eternal vacation.

Medusa
Medusa was a beautiful but power-hungry mortal girl. When she met young Poseidon, she realized that was her chance to make a god fall in love with her, so she can gain some of his power; Unfortunately, Poseidon fell for her trap and gave her powers. When he realized that she tricked him though, he cursed her to change into a monster. Medusa gained the power to destroy everything or everyone who crossed her path but also swore to take revenge on the one who cursed her.

Ocean
Grandfather Ocean was the Sea ruler before Poseidon inherited the Underwater Kingdom. A Titan himself, he’s so old, he can’t wait to retire. When Poseidon visits him to take advice on his new duties, Ocean realizes his grandson does not believe ruling the seas is important. Ocean then gives Poseidon a much-needed prep-talk and a very special gift (and a powerful weapon); the Trident of the Seven Seas.

Amphitrite, Nereus, and Triton
Amphitrite is a young Sea Nymph and an aspiring marine biologist. She arrives at Calypso’s island with her two friends, the sea god Nereus, who’s studying to become a sea vet, and the sea god Triton, who’s studying to become a famous musician. Her mind only set on her studies, Amphitrite has come to the island to study the coral reef’s wildlife. Her determination, creativity, and sense of responsibility will wake Poseidon up and make him realize it was a mistake to give up his duties.

Proteus
Proteus is a Sea God who is extremely lazy and has been residing in Calypso’s island with no intention to interrupt his everlasting vacation anytime soon. He is completely taking advantage of her oath to accommodate gods and immortals and he tries to convince Poseidon that, living in his own bubble is the solution to all his problems. It’s all about having fun and having no responsibilities to worry about. At first, Poseidon tries to adopt that mentality but eventually realizes otherwise.

Rhea
Rhea is Zeus’, Hades’, and Poseidon’s mother. She favored Zeus when he was a baby (he was the one she chose to hide away from his crazy father, Cronus), but she has recently realized that Poseidon is the one who really cares for his mother. Knowing she wasn’t fair to him when he was only a child, she tries to make it up to him by supporting him and defending him against his brothers’ bullying. Soon, her love, care and support lift Poseidon’s spirit and make him the most powerful of them all.

The Harpies (Lithi, Zilia, and Electra)
The Harpies were originally vultures, feeding off of animals’ and people’s dead bodies.
When Medusa encountered them, she felt sorry for them and turned them into bird-women, the sinister Harpies. Since then, the Harpies serve Medusa as their Mistress and they fly far and wide to give her all kinds of information and do all kinds of malicious acts on her behalf. They are the ones who bring to her Poseidon’s lost Trident.

The Mermaids (Hydra, Almira, and Cyana)
The Mermaids are the sea nymph Calypso’s companions and co-workers, at Calypso’s Spa and Resort. They are the ones serving the guests and making sure they are accommodated properly. Although one of them, Hydra, is fed up with pampering lazy Proteus, when Poseidon arrives on the island she becomes star-struck with him and his greatest fan (mainly because of his looks). These mermaids are boy-crazy, vain, and not particularly bright.