A Mount Maunganui man has been flown to Devonport naval base hospital with a suspected case of the bends after diving near the wreck of the Rena.
The 68-year-old was flown to the naval base by the TrustPower TECT rescue helicopter for specialist treatment.
Rescue helicopter pilot Liam Brettkelly said the man had been diving off the Tauranga coast on Sunday afternoon but began to feel unwell after surfacing.
"He said to the nurse it was like the worst hangover he's ever had, but without the drink," Mr Brettkelly said.
The man went to hospital about 11pm on Sunday.
Mount Maunganui Underwater Club patron Russ Hawkins said the man was an experienced diver.
"He's very experienced. I would say he's been doing it for a long time, about 40-odd years I would say. It [the bends] doesn't happen very often ... [but] we're not sure this even is a 'bend'. It's hard to say," he said.
Mr Hawkins said the man had most probably been diving for crayfish at Okaparu Reef.
The TrustPower TECT rescue helicopter flew at least one or two divers suffering from the bends to the naval hospital every year, Mr Brettkelly said.
"It's the only place [to go for treatment] apparently."
Decompression sickness, or "the bends", occurs during a dive when nitrogen bubbles are absorbed into body tissue and the bloodstream. In extreme cases, divers can die if untreated.