A search and rescue operation is underway for a missing swimmer.

Emergency services were called about 6.30pm on Thursday after the man failed to resurface after going swimming in the Waikato River.

'Initial reports indicate the man had been on the river bank with two others before he entered the water for a swim, near the Rostrevor Street jetty,” says a police spokesperson.

'Police have conducted river searches by boat and jet ski, however, these have been unsuccessful.

'Searchers will continue their efforts today.”

The Police National Dive Team has been advised and is expected to join the search today.