Swimming... in Australia

It's a warm sunny day at one of Australia's many beaches. The continent is covered with beach after beach and now it's time to take a swim in the ocean. Stop! Are you at the beach during the day? Is it a public beach? Is the year between 1838 and 1902? In Australia, it was illegal to swim at public beaches starting in 1838. Luckily, the law was only upheld until 1902. (http://www.convictcreations.com/culture/facts.htm)
How and why would such a law be passed? At that point in history, many online articles hinted, that it was related to the newness of the country. It was a time when many of Australia's inhabitants were convicts. They also said that none of the convicts could bathe in the beach water during the daytime. Truly, times in Australia have changed, but this law sure proves to us how the transformation continues to grow.