Elsword only knows the most basic of swimming - the sort you’d use to get across rivers, or try not to drown if you fell into a pool in the White Mist Swamp. He looks quite uncomfortable in the water.
Aisha definitely knows how to swim and is not using magic to make the water help her. She has her staff in the water just because she wants to. Strangely enough, though, if you take the staff away, she sinks like a stone….
Rena is a graceful swimmer. She doesn’t like going underwater fully, but she does like floating on the surface.
Raven cannot be persuaded into water that’s more than waist-high. He used to be a good swimmer, but with all the metal in his body, it’s hard to keep him afloat now, plus the Arm tends to throw a hissy fit whenever he gets it wet. He’d rather just avoid all that hassle and not swim.
Eve is pure metal and cannot swim. She’ll correct the rest of the Elgangs’ swimming technique, though.
Chung grew up as the prince of the Water El’s territory. Of course he can swim. He’s good at it, too, staying underwater for long periods of time with his eyes open. It’s really obvious he’s been swimming all his life.
Ara flails in the water, panicking for a few moments before she realizes it’s shallow enough to stand. Eun despises the water and constantly needles at Ara to get out and get dry. Ara obeys mostly because she’s afraid of drowning.
Elesis has a natural disgust of water courtesy of the fire running through her veins, but once she’s in, she doesn’t seem to mind it. She’s that one person who splashes others and starts fights.
Add’s Dynamo don’t work well in the water, therefore, the only way to get him swimming is to literally push him in. However, once he’s in, you’ll have to pull him out - Add has no clue how to swim.
Lu doesn’t exactly know how to swim - there’s no water you’d want to cover yourself with in the demon world - but it looks fun, so she’s eager to learn. Ciel gets a nosebleed from seeing her in a floaty tube.
Ciel only knows the bare utilities of swimming, mostly because some of his assassination jobs required him to get close to his target via water. He’s still somehow graceful while swimming.
Rose used to like swimming to relax. After Hamel, and all the water monsters there, she no longer likes it.
Ain is confused by swimming, but he watches Chung and picks it up quickly. He ends up being the one to teach Elsword how to swim properly instead of frantically doggy-paddling.