His senior debut came during the 2013 Vodacom Cup competition, coming on as a substitute in 17–17 draw against in Ceres. Seven more appearances followed in that competition. He was then included in the Western Province's Currie Cup squad for the 2013 Currie Cup Premier Division competition and made his Currie Cup debut against the, which also ended in a draw, the final score being 31–31.
Sharks
He joined the at the conclusion of the 2013 Currie Cup Premier Division season. He played in five matches for the in the 2014 Vodacom Cup competition, finishing as top-scorer for his team with 53 points. Swiel was also included in the squad for the 2014 Super Rugby season. He made his Super Rugby debut, replacing Patrick Lambie in the sixth minute of the Sharks' match against the in Pretoria. He scored his first points in Super Rugby just three minutes after coming on, converting a Willem Alberts try. A month later, Swiel made his first start in Super Rugby in their home match against the. He made his second start the following week, where he scored all his side's points in an 18–34 defeat to the. Swiel made a total of six appearances during the season and scored 38 points as his side finished top of the South African Conference before losing to the in the semi-final. In September 2014, Swiel made his Currie Cup debut, playing off the bench in their match against. He started their next match against the in Bloemfontein and also played against the. In addition to his three Currie Cup appearances, he also played for the side on six occasions during the 2014 Under-21 Provincial Championship, scoring 38 points.
In October 2014, English Premiership side Harlequins signed Swiel as short-term injury cover for Ben Botica. He made his debut for Harlequins in their LV= Cup match against Saracens, coming on as a second-half substitute. He made his starting debut a week later against the Newport Gwent Dragons in the same competition. After making his Premiership debut against Bath, he also made his debut in the European Rugby Champions Cup, playing in both legs against Irish side Leinster, as they finished third and failed to qualify for the knockout stage. He made a total of ten appearances for Harlequins during his loan spell – starting five of those matches – and scored 75 points before returning to the Sharks before Round Three of the 2015 Super Rugby season. In April 2015, Harlequins announced that Swiel would return to the club on a full-time deal for the 2015–2016 season.
In 2018, Swiel moved to Premiership side Newcastle Falcons.
Representative rugby
In addition to being included in the South Africa Schools side in 2011, he was also included in a South Africa Under-20 training squad, but later ruled himself out of selection for the 2013 IRB Junior World Championship. Under IRB rules, playing for the S.A. Under-20 team would have made him ineligible to play for another international team, but as a British passport holder, Swiel wanted to keep his options open and did not yet want to commit his long-term international future to South Africa.
