As Elsa and Moana are from different series, and have never met. While the film Ralph Breaks the Internet does have online versions of the two known as "netizens", where they are two of the Disney Princesses that are from the website, Oh My Disney. In the film the netizen versions of Elsa and Moana were briefly seen talking to each with Anna, before Vanellope got into the princesses' dressing room.
At the beginning of their films, both girls were seen as children before the timeline of their childhoods jumps to the main events of their stories. As the daughters and heirs of their people's leaders, both Elsa and Moana were told to be perfect and have tried to be so for their father, even though what makes them different from the people around them makes it a bit harder for the two. Due to Elsa's ice magic and Moana feeling drawn to the ocean, while Elsa's watery connection is mainly of frozen water until she meets and tames the water Nokk in Frozen II, they both have their own kinds of connection to water. Like both of their homes being surrounded by it. Because of past events, their fathers have kept them from who and what they love for their Elsa and Moana's own protection. Even though Moana was able to change her father's mind about the ocean after she made it safe for all again, the death Elsa's father had prevented him and wife from seeing the moment where their eldest was able to regain control of her powers again all while reconnecting with Anna.
The two have also became the recent new leaders of their people. Even though Elsa was crowned in the beginning-middle of Frozen before Frozen II has her bequeathing it over to Anna after she became an ice spirit, while Moana became her tribe's new chief at the end of Moana. Just as Moana is friends with the ocean, through conscious of the watery element itself, Frozen II had Elsa encountering, facing and even calming a wind version of Moana's watery friend, Gale the wind spirit who takes the form of the very wind that blows through the Enchanted Forest. Along with the Nokk turning itself into water in which allows the water spirit to flow with the Dark Sea's current, whenever it doesn't take its stallion form. Thought Moana's journey on the open ocean, wind is one of the main elements she realised on to feed the sail of her small boat. While the Earth Giants are similar to Te Fiti, the Island Goddess that Moana bonded with after she returned her stolen heart. As their own connections with mystical fire, Elsa's is with the small fire spirit that she befriended and nicknamed Bruni, even though the name wasn't mentioned in the film, while Moana's was with the lave demon Te Kā who she had helped to become Te Fiti again.
The snowflake necklace that Elsa wears with her white ice spirit clothing is similar to the necklace that her mother's young self was seen wearing. While Moana's signer necklace was given to her by Gramma Tala on her death bed, so her granddaughter will be able to keep the Heart of Te Fiti safe on her journey.
The ship is believed to have began sometime around the release of Moana. After the release of the teaser Frozen II trailer, it had inspired fans to make fan-made work of Moana helping Elsa during or after her failed attempts to run across the ocean's surface. Like how Elsa and Anna, Moana was also added to the fandom, giving it it's second renamed title Rise of the Brave Tangled Frozen Moana Dragons. The growing RotBTFD fandom crossover has also placed the two, along with Rapunzel, Merida and Anna, in a sup-expanded CGI Disney Princess crossover of the fandom that goes by the three commonly used names of The Female Four, The Four Seasons and the CGI Princesses.
Just as the water scene from the Frozen II trailers have gotten fans to add Moana in the scene through their fan-made work, Elsa's flowery dress in Frozen Fever and the style of a few of Moana's clothes have gotten a few fans to create manips of Elsa wearing her green dress or the flowers that are part of their design whenever they have her with Moana in their ship supporting work. Along with using screenshots and renders of Moana or any of the other people from her Disney film, so they can feature Elsa as a fellow Wayfinder or a member of Moana's tribe. Their have even been a few fanart manips and artwork of Moana in Elsa's main blue dress, and vice-versa, for fun.
A modern AU sometimes involves the two in their outfits from Ralph Breaks the Internet. In a few other AUs, Elsa and Moana have been cast as Marinette and Alya from Miraculous Ladybug. Along with a elements AU giving both girls elemental powers, even though Elsa already has powers over ice and snow a few fans have given her powers over water, which is Moana's commonly given element in elemental related AU, like the Avater series fandoms where they're both commonly seen as waterbenders. Along with Frozen II giving Elsa a few Avatar-like traits, in which could easily have Moana as Elsa's waterbending teacher.
Because of the "Os" in their film's titles, along the snowflake pattern and design on Elsa's blue sets of clothing and the swirl on both the Heart of Te Fiti and the sail of Moana's sailboat, a snowflake is seen as Elsa's personal mark while the swirl is viewed as Moana's. The two marks are sometimes placed beside each other alone or when they featured on or above Elsa and Moana, among the other princesses and their own marks.
On AO3, the ship only has 10 fanfics, while fanfiction.net has 2/3.
- The unknown girl that is seen in the teaser trailer of Frozen II, before she was revealed to be a young Iduna, looks a bit like Moana.
- They are both two of the limit time characters in Disney Magic Kingdoms.
- They are two of the Disney Princesses without a love interest, like Merida from Brave.
- Moelsanna refers to the ship between Moana, Elsa and Anna