The heavy spear-tipped anchors are used to hold 1m triangular race buoys in position in the sand.
Sandi Keen, race secretary, said race crews and organisers were busy setting out the course when suddenly Mr Appleby held his arm up out of the water and called for help.
She said about 20 fellow racers rushed out to help and carried him up the beach to meet the lifeguards who were coming down with a stretcher.
About 50cm-1m of intestine was hanging out, she said.
"There was a decent amount. It did look very gruesome ... I couldn't see if it was just a puncture or a gash.
"He was in a bit of shock but he was doing the right thing, he knew just to hold it. He was coherent, he was breathing and talking properly [but] he was pretty white.
"Accidents like that don't happen very often. It was a freak accident, the waves came at the wrong time."
Four lifeguards responded to the incident, staying with the injured man until an ambulance arrived. A Tauranga St John spokesman said the man was taken to Tauranga Hospital.
At Tauranga Hospital, Mr Appleby was rushed straight into theatre for surgery.
A hospital spokeswoman said he was in a stable condition this morning.
