The evergreen Tony Fantham will contest his 11th swim at 78, while Margie Chiet is also a regular aged 69 this year.
Fantham has won the oldest male division six times, while Chiet the female section just four.
"In the old days there was only an oldest swimmer division and I won it most times because I was older than Margie, so I decided to donate a female trophy and she has now won it four times," Fantham said.
"It was one of my old boxing trophies and I call it Margie's cup now."
Chiet's story is one of courage and bravery.
She has competed despite one hip operations, two knee replacements and two shoulder operations that forced her to virtually one-armed last season.
The event started in the 1930 and had a 29-year hiatus between 1967 and 1996 when it was relaunched. There are now seven trophies up for grabs between and age group and wetsuit/non-wetsuit divisions.