Just a note, it is illegal to collect any livestock from reefs around singapore. Even a dead shell is not allowed.
Chek Jawa broadwalk is open to public but not the intertidal area. You need NParks approved personal to bring you down. Normally, this is done during their public walks. Do check http://www.wildsingapore.com/ for more information
If anyone is interested to view rich biodiversity in Singapore reef, do sign up the various walks offered by various organisation (NParks, RMBR, Etc). They do conduct regular visit/walks to places like Chek Jawa, Pulau Semakau, Labrador, etc.
Cheers