Patrick Junior Meafua's body was found on Tuesday, three days after he slipped off a pontoon and disappeared into the murky Brisbane River.

The 23-year-old was with family and friends celebrating a 21st birthday near the Jindalee boat ramp when he slipped from a pontoon into the water around 5.40 am.

The young man, who couldn’t swim, failed to resurface.

Patrick's sister Martha Meafua posted on Tuesday that their family asked for privacy as they prepare for their beloved brother's homecoming and final services.

"It is with great sadness to announce the passing of our dear brother, son, uncle, nephew and friend, Patrick Junior Ueni Meafua. Our family is devastated and we ask for privacy as we prepare to bring him home," Martha said.

"On behalf of our family, my parents and siblings. We want to thank and give our utmost appreciation to the community for their outpouring love throughout the past few days stopping by with food, drinks and words of comfort."

Martha also thanked the volunteers, SES, police, water police, Marine Rescue, Dive Squad and Australian Water Force services for the help, support and efforts in trying to find Patrick.

One family member, Helen Manu said her heart aches for the passing of her baby cousin.

"This is very sad news, oh my poor baby cousin, our American baby," she said.

Another woman on social media sent her condolences saying this was tragic news and says everyone needs to know how to swim in this generation.

Nearby boaties quickly rushed to the scene in an attempt to help.

“A couple of (the missing man’s) mates actually tried to help, but he slipped below the water before they got to him,” Queensland Police Service Acting Inspector Shane Thow said.

A man in his 20s, who had jumped into the river in an attempt to help, was injured and taken to Queen Elizabeth Hospital with a shoulder injury.

The search involved Water Police, Dive Squad, general duties police, SES, Marine Rescue and aerial assets, who worked tirelessly for three days to locate Patrick, police said.

The body was located downstream, within the search area, around 8.30 am Tuesday.

Patrick's uncle spoke to 7NEWS, warning of the dangers of water and urging caution near boat ramps and rivers.

Patrick’s father, Patrick Meafua Sr, devastated by the loss of his son, expressed his gratitude to the rescue teams for their relentless efforts.

Patrick's family said they will announce details of his funeral services in the next few days.