Introducing the rock stars of the ocean

And there's never been a better time to witness these spectacular and colourful creatures, who "live fast, die young", in their natural habitat than in the waters of the Upper Spencer Gulf Marine Park near Whyalla.

Each year during June and July, the waters around Point Lowly are filled with thousands of giant Australian cuttlefish, with larger males the size of a medium-sized dog, measuring up to 60cm and weighing around 5kg.

Department for Environment and Water spokesman Chris Thomas said the cuttlefish start to congregate to breed in mid-May but the best time of year to experience them is June and July when the breeding season is in full swing.

"The waters around Point Lowly have rocky seabeds, which provide the perfect environment for females to lay and delicately attach their eggs," Chris said. "As part of their breeding, the males put on a spectacular display of colours and shape-shifting to attract and keep a mate."

Chris said swimming with large cuttlefish could be first be intimidating, but after a few minutes people realised they were oblivious to their presence.

"There is one thing on their mind - procreation."

He said numbers have increased since a record low of just under 13,500 in 2013 compared with just under 128,000 recorded last June.

You can see the cuttlefish up close by snorkelling or diving in waters around Point Lowly, also known as Cuttlefish Coast.

At Stony Point, about 20km north-east of Whyalla, there is easy access via a boardwalk to shallow water.

The next best spot is nearby Black Point. You will also find shelter from a north or north-easterly wind on the north-west point of Black Point.

The cuttlefish are active day and night, but the best time to swim with them is in the morning before the winds pick up in the afternoon.