There’s one onsen with couple room onsen near joo koon mrt. I have been there twice before. The water was not bad, it is renovated from an existing swimming pool, partitioned into smaller rooms. There’s steam room within the couple room also. I think usage is 90 mins or 120mins. The water fountain and splashing is noisy enough to cover any hanky panky u want to do inside. But i dont recommend. Cos the floor and steam room bench is hard
Even if u want to do doggy in the water is also not recommended. U will feel light headed after prolong submerging in onsen. Tried and tested.