Only parts of the island was swampland doesn't mean all was swampland lah!
You should read the first one or two chapters of this book, which describes the situation, with statistics from Sinkieland own Government archives, just before independence, which was very rosy by Southeast Asia standards - per capital GDP second only to Japan in Asia. Almost self-sufficient when it comes to essential foods such as poultry and vegetables - that was a surprise to a kid like me who was indoctrinated from PAP kindergarten. It should be available in Kiwi-land. Those in Sinkieland can buy from Amazon or Johore Bahru.
http://www.amazon.com/The-Singapore-Miracle-Myth-Reality-ebook/dp/B00DPK9DUU