Magazine editor Denise Li has been practising martial arts like muay thai, boxing and Brazilian jiu-jitsu since 2009, sometimes training up to five times a week in Brazilian jiu-jitsu.

After falling victim to frequent injuries, however, the 34-year-old took a break in May and went on a lookout for "a workout that was a little bit more intense, but wasn't too hard on the joints".

She found what she was looking for about three months ago when she picked up HydroFit, an adapted version of stand-up paddling (SUP) yoga, from instructors at local company The Fitness Project. It was started in April by former national water polo players Lim Yao Xiang and Teh Chong Nyen.

SUP yoga, usually conducted in open water, is offered by several gyms and schools here like Stand Up Paddling School and SUP Yoga Singapore.

HydroFit workouts are done on Boga floating fitness mats in swimming pools.

Another local fitness company offering similar exercise classes is Skyline Aqua, whose sessions started in September. These workouts called FloatFit originated from English company aquaphysical and use AquaBase mats.

It conducts about 14 sessions each week at Parkroyal Beach Road and has secured a second venue in Safra Tampines owing to "overwhelming response", said its director Jeniffer Song, 37.

"Our revenue doubled from September to October, and the take-up rate for November has increased as well," she added, estimating that participants have increased from 75 in September to 300 in November.

The Fitness Project conducts two classes each day with five to six people per session, according to Lim.

Sessions have been held at Chinese Swimming Club since lessons began officially on Sept 1.

From next month, there will also be two regular sessions at the OCBC Aquatic Centre as one of the Sports Hub's aqua-fitness classes: the Pump, where exercises like push-ups, sit-ups and squats are performed on the mats, and the Zen, which involves a combination of yoga-and pilates-inspired moves.

Lim, 35, said he and Teh wanted to introduce the activity to the masses as they wanted Singaporeans to enjoy working out as much as they do. They decided that it would be suitable in a country with a lot of swimming pools and a large population of people doing yoga.

"It's not new in terms of the kind of exercise, it's just about adding a twist to what already exists in Singapore," he added.

One key benefit of such workouts, said Lim, is that doing the exercises on a platform which moves on water ensures that the smaller muscles commonly neglected by participants are engaged. This can help prevent injuries.

"When doing the exact same exercises on land, such as regular yoga, you can 'cheat' in the sense that the floor doesn't move so you can compromise your body position to do a certain pose," he explained.

"But on the water, once you lean too much on one side, it shows on the mat and it starts to rock. So you really need to control and stabilise the supporting muscles.

"Even for a simple squat, maybe on land you can lean a bit more on your right side, but you can't do that on water."

Li believes her balance has improved since she started HydroFit classes, although she was initially hesitant about the possibility of constantly falling in the water.

"The board is a lot more stable than I thought, but at the same time it was very challenging because you don't realise you're using all those muscles to stabilise yourself," she said, adding that she was less fearful once she realised falling in the water was the worst thing that could happen.

Tour guide Shirley Sim, 58, tried HydroFit pump for the first time on Dec 11 and was hooked.

"It was interesting and something special to have a real workout on the mat floating on water," she said. "The next day, I could feel my thighs aching.

"This is something that is not the same as what I usually do (swim on alternate days in the evenings).

"I like water sports and this kind of aqua activities."

Lim, who won SEA Games gold in fin swimming at the 2003 Games, said a common misconception about HydroFit is that people think they can participate only if they are expert swimmers.

"The only swimming involved is swimming out to the lane to get onto the mat," he said.

"You don't need to be a great swimmer but you need to be confident in the water and cannot be afraid of water."

• Participants must be aged 18 and above. For more information, visit sportshub.com.sg