I know what you're thinking: "Well, she's obviously on land, so she can breathe air, duh!"

But notice those water particles under her tail? Makes me think that she's using magic to enable movement on land, rather than having that ability naturally. Maybe it's the same for her ability to breathe?

She's Avian, fool. I got 10:1 odds she floats in game.

She's aquatic.

On the field her movement speed is 5 unless she uses "flop" to propel herself awkwardly down the lane.

It's clear to me, from the blue particles underneath her, that she IS using some form of magic to move on the land via having water propell her because she can't use her fin to move on the ground comfortably.

However, she MAY be able to breathe air naturally (being a mermaid, which MAY qualify her to be amphibious) OR she may be having to use her own magic/Summoner magic to help her (we'll have to wait for the lore to see).

If I had to guess, though, I'd say that she's aquatic, as she lives all her life in the water (well, save for the game), with the ability to breathe air naturally (from her mermaid genes).

I'd like to introduce you to the lungfish.

The only real question I have is how is she going to move around. Personally, I think it would be hilarious is she just flailed around the ground.

How come Zilean floats? How come Anivia is able to fly throughout the entire battle? How come Urgot's legs never run out of gas? How come Malzahar is able to float and Ryze isnt? How come Xerath gets stronger when standing still? How come Fizz doesn't swim in the rivers? How come MF gets faster by "struttin her stuff"? How come the shop guy doesn't give away stuff for free? How come Teemo is able to find explosive mushrooms every 30 seconds without actually looking? Warwick can't smell jungle creeps? How come Jax/Maokai are able to move farther with their abilities if their opponent flashes? How come Amumu kills people by crying? How come Nasus loses all of his Siphoning Strike power every game? How come everyone starts off at lvl 1 every single time? How come Swain doesn't fly around when he uses his ult? How come Graves is able to run through walls and flying characters cant just fly over them? How come Morgana can't fly and Kayle can? How come Nautilus doesn't just drop his anchor and swim all over the fields of justice? He doesn't need the anchor for anything but his basic attack. What I'm getting at is that Summoners are freakin OP, and the Laws of Physics do not apply to them.