The six women (out of ten members of staff) were stunned when they discovered all of their babies are due within four months of each other.
One of the mums who is expecting, offered a suggestion as to why she and so many of her colleagues all fell pregnant.
Karina said: "Watching babies in the water every day with their parents just makes us broody.
"It's such a lovely environment and I think it just makes us all want to experience it again.
"Everyone finds it funny that we all seem to have fallen pregnant at the same time. We just keep adding someone else to the pregnancy list."
As well as the six members of staff being pregnant, a seventh member is currently on maternity leave after recently giving birth to a baby boy, named Samuel.
One of the expectant mothers' bosses, Karina Reinhardt, 36, said she has no concerns about covering classes while the mums are on maternity leave.
"We hold aquanatal yoga classes for pregnant woman and we were all joking that there would be no room left in the class for anyone else."
Reinhardt is hoping to recruit two new teachers and another administrator to cover the business in her current employees' absence.
Turtle Tots, which began in 2012, provides classes to teach babies and young children to swim. The lessons begin during pregnancy and continue once the baby is born.