Over a 24-hour period on Monday, the New South Wales State Emergency Service rescued about 34 people, many of whom had deliberately entered floodwaters by foot, car or boat, despite warnings to stay away from nominated roads and beaches.

The following incidents occurred when people chose to test nature's force:

■An experienced surfer, in his 60s, mistimed his jump off the rocks at Avalon Beach on Tuesday morning and was washed back onto the rocks. Paramedics treated the man for suspected spinal injuries and for lacerations to his head. He was taken to Mona Vale Hospital for further treatment.

■A couple on a boat near Elizabeth Island, Grafton, ignored advice from the SES on Monday to leave or move their vessel because they were in an unsafe area. Their anchor broke and the couple had to be rescued by an SES flood boat at 4am on Tuesday.

■In Lismore, three rescues took place on Monday evening for people who had driven into floodwaters and become stuck. As the SES team finished one rescue, they were called straight to another without time even to return to base.

■Stormy weather did not deter one man from canyoning in the Blue Mountains on Monday night. After a search-and-rescue mission, the 26-year-old was found on Tuesday morning near Bowens Creek and treated for mild hypothermia and dehydration. He set off a personal locator beacon in the Mount Wilson area just before 7pm on Monday.

SES spokesman Philip Campbell said more than half the people rescued had entered the floodwaters against advice. He said the consequences could be ''deadly serious'' as floodwaters can be deeper or faster flowing than they appeared, with the further dangers of debris, chemicals and viruses.

''Our volunteers love helping people, they're not judgmental, but there is a degree of disappointment that we have with people who make a decision to deliberately enter into water.''

Another member of the SES, Samantha Coluell, expressed frustration at people who put lives at risk and did not heed advice. ''We have had a couple of people that didn't evacuate until water went in their door,'' she said.

Surf Life Saving NSW spokeswoman Donna Wishart advised people to stay out of the water on Tuesday, including experienced surfers who have been heading out despite many beaches being closed. Although the surfers wanted to take advantage of the big surf, they fell into danger when they underestimated their abilities or the conditions, she said.