Sungei Buloh Nature Reserve (Mangrove Swamps, bird watching, swampy forest life)|
Pulau Ubin (canoeing, mountain biking, old quarry and island life)
East Coast Park is not that bad as a manmade beach
If you have a car, take a ride to Jurong island where all the refineries are, it is a nice tour and good views of the sea and our neighbouring countries.
There are a few resevoirs that offer nice walks in the late afternoon.