The Spanish striker, who joined on a season-long loan deal with a view to a permanent move, sealed the switch late on deadline day to become Michael Laudrup's ninth signing of the window.
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|16/1||Swansea are 16/1 with Coral to finish in the top six
"This is a really good opportunity and I will try to make the most of it this season," he told the club's official website.
"I know a lot about Swansea, not just the club, but the players as well. They have a lot of Spanish players that I was aware of, and of course Michael Laudrup as well.
"I'm also aware of the great season that they had last year and now they are playing in the Europa League as well. I have never played in that competition and I'm really looking forward to it.
"It's an honour for me to be here and I will try to do my best and repay him (Laudrup) for showing faith in me."
Vazquez will hope to make his bow for the club when they come up against Liverpool at home on September 16 before visiting Valencia in the group stage of the Europa League three days later.