"Long before Sir Stamford Raffles landed on Singapore, there were native aboriginal coastal dwellers living at the mangroves areas at the mouth of the former Seletar River (now Lower Seletar Reservoir). The natives were known as orang laut, and ones living at Seletar were called orang seletar. When Singapore was part of Malaya, these orang seletar roamed freely in the Johor Straits, between Pulau Seletar and the southern coast of Johor. When Seletar became inhabited by other locals, orang seletar were shifted to Sungai Pulai of southwest Johor by Sultan Abu Bakar."
If you are visiting the internal part of the fishing village, you can ask the dwellers staying there. They are all very nice people and usually they will allow you to enter their compound.
Do check the tide-table and wear proper foot-wear as the area is full of hazards on the ground.
Warning : do not enter those "unauthorised area" demarcated by the law !!!