While she is a Mermaid, Ariel has a few abilities.
Atlantean Strength: She is known to have at least a very certain degree of Atlantean strength, as she was able to move away from an underwater boulder blocking her grotto with relative ease in the original film. When discovering Eric's ship due to the fireworks, she is shown effortlessly climbing up the side of the ship with just her arms. When saving him, she effortlessly pulls him towards the surface and manages to keep them both afloat while holding him with one arm. In Ariel's Beginning, she seemed to be able to knock down a door to free her friends (This is especially telling as Sebastian stated immediately prior that she was "a weak helpless girl"). It's debatable if she ever retained her Atlantean strength by the time she became a human.
Alantean Endurance: Ariel may also have Atlantean endurance, as, during the final battle with Ursula in the film, she was at one point knocked into a whirlpool that is several miles deep and survived with barely any injuries. Such a feat would kill a normal person if not completely destroy the body of a said person. Like her Atlantean strength, it's debatable if she ever retained her Atlantean endurance when she turned into a human, although her first transformation implied that it was retained as her body was not being crushed while trying to swim for air.
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Speed Swimming: Also, Ariel is capable of swimming at a much faster rate than humans or even certain marine creatures in terms of undersea travel, or sea travel as a whole due to her half-marine status. Like dolphins, she is capable of leaping out of water at great heights. For example, she was able to get to King Triton's palace from Prince Eric's kingdom in less than a day, as well as getting from Atlantica to Norway in the episode "Metal Fish" in a similar time fashion.
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Thermoendurance: Ariel has demonstrated the ability to endure temperatures far more extreme than would be survivable for a human (especially one of her build). This is shown in the film's and TV series, where she went to the arctic with minimal ill effects other than feeling a bit cold, as well as in Return to the Sea, where she traveled to Morgana's lair, which was located inside an iceberg, and when visiting Ursula's, which was located in a volcanic region.

http://disney.wikia.com/wiki/Ariel
Так вот что за атлант там расправил плечи!