"For the last five years, I've pushed myself well outside of my comfort zone to move to Australia, live by the ocean, learn how to swim multiple laps in a pool, and become a Divemaster," she said.

At first, Srivastava's goal was to complete one lap, but as she improved, the goalpost kept moving. Now aged 75, she can swim much further. "The goal went from to do one lap to doing five laps ...

if you turn up the heat and vigorously swim laps for 30 minutes, your calorie-burn increases. In this case, a 125-pound [57kg] woman will burn about 300 calories a 155-pound [70kg] woman will burn ...