No, it's not a snake casually hanging in an Australian bathtub, but an eastern diamondback rattlesnake at Melbourne zoo keeping fit by swimming against the current. Zoos Victoria

If there is one thing people don't come to zoos to see, it is flabby snakes and couch potato lizards. Melbourne Zoo has found a way to keep its reptiles buff with the creation of a water gym they think is the first in the world. The real value lies not in getting whatever snakes have instead of abs rippling, but in keeping the precious captives healthy and hopefully happy. Sometimes the gym may even be the difference between survival and extinction.

Bathing animals is an important part of zoo hygiene, but Melbourne Zoo realized it could also be useful for dealing with the problem that zoo life can just be too easy for many animals. “A lot of reptiles are ambush predators,” keeper Alex Mitchell told IFLScience. “If they don't have to chase their prey they become sedentary and quite prone to obesity.”

Starting out by trying to get snakes to swim in a bucket, Melbourne Zoo gradually upped its game to eventually produce what Mitchell described in a statement as “a temperature-controlled, filtered body of water, which allows keepers to manage water flow through the tank.”

The current flow is adjustable, allowing a gentle introduction. As animals get used to the idea, the current can be turned up to create a sort of watery version of a treadmill. However, Mitchell told IFLScience, "the animals don't just go against the current, sometimes they swim with it. It creates novelty,” and opportunities to play.

Or, as Mitchell puts it, it's “sort of like aqua-aerobics for reptiles.”

Most animals enjoy a 4-5 minute swim before showing signs they are tired, at which point the keepers scoop them out. On the other hand, eastern diamondback rattlesnakes prefer extended time in the water, and no one is game to tell them no. Some animals chill out on a platform when they feel they have had enough exercise for the day, while the snakes move out of the main current to where still water makes swimming easier.

Among the species benefiting is the golden coin turtle, whose critically endangered status means each individual needs to be breeding for the planet. The unfortunate turtle is in such demand for Chinese medicine that individuals can sell for thousands of dollars. If a nice dip gets the turtle juices flowing, the hydro-gym will have been well worth it.

Sadly, there are only limited opportunities for the public to watch the fun, but staff hope the idea will catch on and other zoos will start to install similar facilities.