The 20-year-old wing back is showing his best qualities in the Championship with the Welsh club, following a loan spell in the second half of last season with MK Dons.
He played for now Swansea boss Russell Martin at MK Dons, with the duo reunited this season.
"I had a brilliant chat with his dad when he signed here. His dad is really grateful for the amount of work and time we've put into Ethan and how we treat him as a person. He's really grown up.
"He's a brilliant character, a real extrovert, a really confident lad in a humble way. He's brilliant for the group, especially the young guys, because he's an old head on young shoulders.
"Regardless of the game, he plays with real intensity. He's got a bit of swagger, and it comes from a big club. But, again, it's in a respectful way because he just wants to be a good player.
"We've loved him from day one at MK Dons, he was brilliant for us there, and that was why we were so keen to get him here.
"He had a lot of interest from this league because of what he did last year, and the only reason he came here is because he trusts us, he enjoys working with us, and he understands his role really clearly. So I'm really pleased we got him, and he's showing now what he can bring, but there's definitely more to come from him."
Asked how Manchester United felt about the move, Martin added: "They feel it's a really good place for Ethan to keep developing and learning, and so do we.
"As long as he can keep doing what he's doing, train hard, and he's finding some real consistency now, which is really nice.
"I think the fans are enjoying him, the boys are definitely enjoying him, and that's what it's about."
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