In October 2018, he represented South Korea at the 2018 Summer Youth Olympics held in Buenos Aires, Argentina. He competed in 50m freestyle, 100m freestyle, 200m freestyle and mixed 4 × 100m freestyle relay events. In the 50m freestyle heats event, he completed at rank 9, allowing him to advance to compete in the semifinal.[1] In the 50m freestyle semifinal event, he completed at rank 8 with Robin Hanson.[2] In semifinal swim-off against Robin, he completed at rank 2 hence did not advance to compete in the final.[3] In the 100m freestyle heats event, he completed at rank 1, allowing him to advance to compete in the semifinal.[4] In the 100m freestyle semifinal event, he completed at rank 3, allowing him to compete in the final which he completed at rank 5.[5][6] In the 200m freestyle heats event, he completed at rank 7, allowing him to compete in the final which he completed at rank 8.[7][8] In the freestyle relay event, the team did not advance to compete in the final.[9]
^Kim, Do-yong (July 27, 2021). "[올림픽] '뉴 마린보이' 황선우, 한국신기록으로 자유형 100m 예선 통과(종합)" [[Olympic] 'New Marine Boy' Hwang Seon-woo passes the 100m freestyle qualifier with a new Korean record (comprehensive)]. Naver (in Korean). News1. Archived from the original on July 27, 2021. Retrieved July 27, 2021.