A chartered catamaran has capsized while on its way back to the Cape Town harbour, it emerged on Monday evening.

National Sea Rescue Institute spokesperson Craig Lambinon confirmed the incident and said everyone on board was safe.

The NSRI said the sea rescue craft Spirit of Day and Spirit of Vodacom were launched.

"Eight persons – three local male crew members and five tourist passengers from the United Kingdom, two males and three females - were found on the upturned hull of the boat. All were wearing life jackets. They were rescued off the upturned hull and taken on board the sea rescue craft and brought to the NSRI rescue base at the V&A Waterfront where all were treated by paramedics for mild hypothermia. Two of the local crewmen were treated for non-life threatening injuries," the NSRI said in a statement.

The catamaran has been towed to a pier in the port in the capsized position and efforts to secure the yacht were made. 

According to the NSRI, the South African Maritime Safety Authority was alerted and the cause of the capsizing will be investigated.

The catamaran operates daily trips and sunset cruises for visitors to the V&A Waterfront precinct.