A teacher has gone missing while swimming at a watering hole in the Northern Territory during a school excursion.
Police have launched a search and rescue operation at Ellery Rock Big Hole in the McDonnell Ranges for the man aged in his 40s.
The Education Department is notifying parents and counselling is being made available for students and staff.
The NT education department said the man was a teacher at the Centralian Middle School.
'The Department of Education understands this incident touches everyone at Centralian Middle School and the entire Alice Springs community,' the department said in a statement.
'Centralian Middle School has additional school counsellors on site and a psychologist for the remainder of the school term to provide emotional support and assistance to all our students.'
All staff will also be provided with access to counselling and support services.
NT government tourist information describes Ellery Creek Big Hole as a deep and potentially dangerous waterhole.
'The water is extremely deep and has been measured at 28 metres in some parts,' a government tourist website said.
'Due to its depth, the temperature of the water can be very low and can be hazardous.
'When swimming it is best to stay in the shallow edges of the waterhole.'
Swimmers are also urged to watch for submerged logs and rocks and are advised not to jump, dive or swing into the water.