Plot

Before a family trip to the Carnival of Tides on the tide, Ariel and Arista get into a fight and are 'beached' and Sebastian had to stay and look after them.

Among Ariel's sisters, the one we know the most about is Arista, if only because Arista can't stand Ariel's headstrong ways. In this episode, Arista and Ariel come head-to-head at last.

It is time for the Carnival of Tides. Everyone in Atlantica is looking forward to it, especially King Triton's daughters because there appears to be something for everyone to do at the carnival. Sebastian has been given the task of gathering all seven girls and getting them ready to leave. Ariel, as usual, is late because she's hanging out with Urchin and Flounder.

As soon as Ariel does come back to the palace, she gets into a fight with Arista. Why? Over a comb that Ariel found and actually belongs to Arista. It isn't really much of a reason to start a fight, but Ariel and Arista don't need much of a reason because they just don't get along. Sebastian tries to get them to stop fighting but fails. When King Triton sees what's up he declares the two girls beached and bans them from going to the Carnival of Tides. Sebastian, of course, is then assigned to be their babysitter.

As you can imagine, neither girl takes very well to this, and they immediately start blaming each other.

It looks to be another boring being-stuck-at-home thing, until the Gators arrive. Specifically, Flo and Ebb Gator, freshwater thieves. Their target is the royal treasure, left unguarded in the absence of King Triton's trident.

Ariel and Arista quickly develop a truce; the Gators are the biggest threat, not each other. If they work together, they can stop the fiends from reaching the royal treasure. Oh, and Sebastian helps, too.

As things go on, of course, Ariel learns that all this while Arista has actually been secretly envious of Ariel's adventures. After all, Ariel gets to do amazing things on a near-daily basis, and although Arista is not quite as outgoing as Ariel, it would be nice to do something amazing once in a while. Brought closer by this admission, the two sisters put their heads together setting up traps for the Gators, so we end up with Home Alone in Atlantica.