De Guzman spent last season on loan at the Premier League club, scoring eight goals in 44 matches, and the former Mallorca player was delighted with his 12 months at the Liberty Stadium.
The 25-year-old told his personal website: "My ears are always open. I had a great year there. The people around the club and the fans treated me well.
"It was not just the results we had, it was more about showing that we can also compete with the big teams. We played better against the bigger teams.
"We played well in a lot of games. We played good football and it's refreshing playing in a team that has a good football mind. I'm very satisfied with what happened. We did very well — we were very creative. We really put Swansea on the map."
De Guzman also broke into the Netherlands senior squad after his performances for Swansea.