The Environment Agency Wales has been undertaking maintenance work at the River Ritec outfall, at Tenby's South Beach.
As part of the company's regular maintenance and inspection of the river outfall, they have employed specialist diving contractors to carry out an underwater survey of the outfall.
This is to check its integrity and to place a new Trinity House standard marker buoy at the end of the outfall to alert boat users of the presence of an underwater obstruction.
This operation formed the final phase of a programme of maintenance carried out during February. The remains of a much earlier outfall alongside the existing outfall were also removed to reduce underwater hazards to bathers and boat users.
Stuart Thomas, operations delivery team leader at Environment Agency Wales, said: "We maintain a wide range of Flood Risk Management Assets such as flood bank, walls and culverts to protect people and properties from flooding.
"This work will ensure these assets continue to do their job of reducing flood risk and that the sea outfall is clearly marked for the safety of boat users and bathers for the foreseeable future."