The upcoming rise in water prices saw about 100 people turn up at Hong Lim Park yesterday to protest against it.
A heavy downpour dampened the start of the protest, which began half an hour behind schedule as people took refuge from the rain and the initial speakers sheltered under an umbrella on stage.
Speakers criticised the Government's explanation that the cost of producing water has risen and that investments need to be made in water infrastructure.
The hike was announced in last month's Budget and will take effect in two phases, starting in July.
The rally was organised by career counsellor Gilbert Goh, a former Reform Party candidate in the 2015 General Election.
Former Singapore Democratic Party candidate Paul Tambyah, an infectious diseases specialist, criticised the timing of the hike at a period of "economic hardship".
He and several others cited comments by Dr Vivian Balakrishnan in August 2015, when he led the Ministry of the Environment and Water Resources.
The minister had said labour and equipment costs had risen since the water price was last raised in 2000, but that there were also improvements in membrane technology and productivity, and given the state of technology and energy prices, there was no need for a price adjustment at that point.
Yesterday, Dr Tambyah asked what had changed since then, noting that Singapore's per capita water consumption had gone down. "Is it (the hike) because of the massive population increase?" he said.
Financial adviser Leong Sze Hian said the Government's reasons for the hike "did not hold water".
The 10 speakers spoke on a small stage decorated with buckets and placards with slogans such as "Pay Until Broke", a play on the initials of national water agency PUB.
They sought more transparency and criticised Environment and Water Resources Minister Masagos Zulkifli's comments in Parliament that he could not disclose details of how the price was computed due to commercial sensitivities.
Others, who included National Solidarity Party secretary-general Lim Tean and former presidential candidate Tan Kin Lian, touched on the Central Provident Fund, living costs and foreigners.