Police hold grave fears for a rower who disappeared after falling into a central Otago lake today.

The man had been rowing on Lake Dunstan, near Cromwell about 8.30am, a southern communications police spokesperson said.

The man had been training on a single rowing skiff when he fell, police said.

Emergency services including police, the coast guard and a helicopter have been searching for the man through the day and the police dive team were on their way to the lake.

Details were yet to be released about the rower.