Lifesavers say the popularity of people jumping from jetties in the summer weather is causing an increase in injuries.
A 50-year-old man was flown to hospital after jumping off a jetty at Wallaroo on South Australia's Yorke Peninsula yesterday.
The man hit his head and suffered suspected spinal injuries.
Shane Daw from Surf Life Saving SA says there have been several severe cases in the last few weeks and people often jump in without assessing the risks.
"We've had a young 13-year-old girl last week who potentially has spinal injuries so had to be treated and taken to hospital," he said.
"We've had some major lacerations and cuts and bruising. We've also had dislocations. We've had broken limbs and we've also then had people who've been knocked unconscious."
Mr Daw says unseen hazards often lurk just below the water line.
"At the jetties we've had out life guards and our surf lifesavers having to remove shopping trolleys that have been pushed over and you can't see those in the water," he said.
"With the tidal changes, we do get sand bars that do move we get high tides and low tides so it can be quite tricky.
"We don't want to be the fun police but we want people to be aware when you're doing that you need to know the risks."
© ABC 2014
16:15 EST The Bureau of Meteorology is warning Sydney and northern New South Wales could be in for another deluge, with a new low pressure system to form off the coast later this week.