Warning signs have been erected at a popular Adelaide beach after two women became trapped in waist-deep quicksand. 

The incidents at Glenelg North over the last fortnight have prompted renewed warnings from authorities about the hidden coastal danger.

TAFE student Madz June, 20, was on a sunset walk with a friend on May 19 when she suddenly began sinking into the sand.

'I just hopped down from the rocks. When doing that my legs fell straight through the sand,' she told Seven News.

'At first I thought it was hilarious… however once I tried to get back out and it was stuck, the panic started to set in.'

She spent the next hour unable to move and had to be freed by emergency responders, who wrapped her in a thermal blanket. 

'I was shaking. I never thought something like that would ever happen to me. It's something that's always going to play on my mind and I definitely won't be jumping from rocks onto sand anymore,' she said. 

Mum-of-two Sarah Darbyshire said she and her dog Bean had a similar ordeal at the same beach on Saturday.

'Bean and I went for a beach walk and somehow ended up in sinking sand. And when I say sinking sand, I mean SINKING, you're going to f***ing die today sand,' she said. 

'Bean almost disappeared first, so I rescued him, launched him onto solid ground, threw the poo bag, shoved my phone in my pocket and then realised I was sinking too. Up to my waist.

'At that point, I genuinely thought, "Well what a way to go".'

Thankfully, pure adrenaline kicked in and Ms Darbyshire managed to drag herself out.

'Life can be beautiful, ridiculous, terrifying and hilarious all in the same day,' she said.

'Sometimes all you can do is keep moving forward, shake off the sand, and enjoy the ride. Me and Mr Bean certainly are.'

Holdfast Bay Council has since installed new warning signs along the shoreline to warn beachgoers of the hazard.

Sand was recently relocated to Glenelg North to raise the beach and protect coastal infrastructure, including properties, from storms this winter.

Quicksand occurs where creeks and rivers flow into the sea, on a beach at low tide, along riverbanks or in rivers with sandy bottoms.

If you become stuck in quicksand, the golden rule is to not panic, according to survivalist Bear Grylls in his book How to Stay Alive. 

'Disturb it more violently and it becomes more viscous, more difficult to escape. That means that the more you fight it, the more it resists you,' he wrote. 

'Each time you pull up your leg, you'll find that suction drags it back down again. You won't drown, but you will be stuck.'

If you have a companion who is not stuck, do not grab their outreached hand. 

'Firstly you risk dragging the other person into the quicksand, which will mean two of you in the same situation,' Grylls continued.

'Secondly, it's easy to dislocate a shoulder if your companion is pulling you one way and the quicksand is pulling you another.

'Wiggle your legs gently to loosen the sand and allow yourself to slowly make your way up and out.

'Make sure you clean yourself off as soon as you can, to avoid being sucked back in at the quicksand at the next available opportunity.'