Ten people had their overnight cruise in Doubtful Sound cut short after three became ill on Sunday evening.
All 10 were removed from Deep Cove by helicopter as a precaution, and the three were understood to have recovered, and continuing their travels yesterday.
The drama began when St John ambulance communications received a call at 5.35pm on Sunday about a group of people suffering an unknown illness on a boat near Deep Cove, in the Fiordland National Park.
Initial reports indicated there were eight patients on the boat.
A St John spokesman said a rescue helicopter was sent, and two ambulances were sent to the wharf at Te Anau.
The rescue helicopter brought the sick tourists to Te Anau in two lots, and they were taken to the Te Anau Medical Centre to be assessed by medical staff.
Deep Cove Charters operator Diane Lemin said the group, all overseas tourists, were on a one-night cruise in the sound, in Fiordland.
Deep Cove Charters is owned and operated by Chris and Diane Lemin, and runs cruises and charters for up to 12 passengers.
Ms Lemin said one person became ill initially, and it was thought the passengers were suffering from sea-sickness.
One of the tourists, a nurse, became sick, and thought the illness might be norovirus, and everyone was taken from the boat, despite some passengers being happy to carry on.
Ms Lemin said she had been to see the ill passengers yesterday, and "all were smiling".
The boat had been "scrubbed top to bottom" as a precaution.
Medical centre doctor Liz Scott said the people suffered from diarrhoea and vomiting but she did not know, at this stage, what had caused the illness.
They had been discharged and the centre had discounted norovirus as the cause.
