Please refer to https://www.moe.gov.sg/news/press-releases/changes-to-direct-school-admission-exercise--for-secondary-schools-dsa-sec-from-2019. All the best
You can start applying for DSA now. It’s online now . Do read this article for the steps : https://sg.theasianparent.com/dsa-2019-singapore
You could also check out MGS DSA as they have swimming as CCA option. All the best:)
Andrew Yap Guan Seng