About once or twice a year, they come together to sing karaoke, play mahjong, exercise and take pictures.
All everyday activities except for one highly visible difference - no clothes are allowed.
And in most cases, no sex as well, said Singapore nudist Roy Tan, who is part of the Yahoo online group SgNudClub.
Naturists, as they are also called, riled the Malaysian authorities earlier this month when they found out that 18 people participated in a so-called sports carnival on a beach in Penang wearing nothing.
So far, eight people, including alleged organisers Albert Yam and Chew Tok Hwa, were arrested.
A check on SgNudClub - which Mr Yam oversees - shows that the group has been around since 2006.
The site is a platform to organise naked events, as well as discuss nudist news, befriend others and share their overseas naturist experiences in, for instance, Hong Kong's Cheung Sha and Pui O beaches.
Tips are shared too. Changi beach, for example, has been ruled out as a venue for skinny dipping because "sea lice can really bite", warned user CH.
Quarrels can happen when a user posts a lewd comment about another's wife.
Nudists whom The Straits Times spoke to said that they believe in the natural state of the human body. They added that anyone can be a nudist, though some groups are more welcoming than others.
"We have married couples, gay men and singles attending our gatherings," said banker Joshua Lim (not his real name), 38, who formed a nudist circle with his wife and some friends five years ago.
The group of 10 go to Thailand about once every month and rent a villa together where they swim, eat and party naked.
"We hardly allow new members unless we have known them for a while," he added.
Such private sessions make it difficult to track the number of nudists in Singapore.
SgNudClub lists over 600 members but "most of them are lurkers" who do not post anything, said Mr Tan.
Members of SgNudClub, comprising mainly Singaporeans and Malaysians, also gather for yoga, kettlebell exercises and nude photography sessions, which are sometimes held in dance studios.
No sex is allowed at these gatherings, which usually take place at someone's place, hotel room or chalet resort.
Each attendee chips in about $15 to $30 to cover the rent. During potlucks, members bring their own food.
Others, such as Mr Bernard Low, prefer to be alone when they are naked.
The 45-year-old architect sunbathes in the nude at home in Serangoon, where he lives with his wife and son. They do not join him, but "accept it".
He said: "Nudism is a personal affair. I will be offended if I see someone without clothes in public too. It's just inappropriate because we live in a civil society where nudity is not the norm."
According to the law, those guilty of public nudity can be charged under Section 27A of the Miscellaneous Offences (Public Order and Nuisance) Act, and be liable to a fine not exceeding $2,000 or to imprisonment for no more than three months or both.