Simon Nellist, 35, was an experienced diving instructor who reportedly posted on Facebook just last year about the impact shark nets had on sealife.
The British expatriate, who was living in the Wolli Creek area of Sydney and was engaged to be married, was attacked by a shark on Wednesday just metres from the rocky shoreline.
Paying tribute, friends said Mr Nellist was “one of the people that makes this earth better”
Della Ross, Mr Nellist’s friend, told broadcaster 7NEWS Australia that he would teach people to “respect the ocean” as it was the shark’s habitat.
“Everything that is connected to Simon, to me is connected to the ocean,” she said.
Mr Nellist is reported to have written on Facebook last August that “shark net and drum lines protect no one and kill all kinds of marine life each year”.
The devices are routinely used in popular swimming and surfing locations in Australia to protect people from sharks.
Conservation group Sea Shepherd Australia describes shark nets and drumlines as “destructive” and claims they have killed “thousands of sharks and rays, hundreds of turtles as well as dolphins and whales”.
The former RAF engineer, who was originally from Penzance in Cornwall, was said to have been training for the 5k Malabar Ocean Swim, a charity event due to take place this weekend, when he was killed.
The event has been cancelled out of respect, organisers said.
Emergency services were called to Little Bay at around 4.35pm local time on Wednesday after reports a swimmer had been attacked by a shark.
Lucky Phrachnanh, from New South Wales state ambulance, said the victim “suffered catastrophic injuries as a result of the attack”, adding there was nothing paramedics could do when they arrived at the scene.
The incident is believed to be the first fatal shark attack in Sydney since 1963.