Ballina Shire’s ocean beaches have received top marks for water quality, but Lake Ainsworth and parts of Shaws Bay continue to struggle as the summer swimming season begins.

The NSW Government’s latest State of the Beaches report rates Lighthouse Beach, Shelley Beach and Seven Mile Beach at Lennox Head as Very Good, meaning they are considered suitable for swimming almost all the time.

Missingham Beach has also recorded a significant improvement, climbing from Poor last year to Good in the latest report.

But the news is not as encouraging at some of the Shire’s enclosed swimming spots.

Lake Ainsworth North, South and West have all again been rated Poor, unchanged from last year.

Shaws Bay West also remains Poor, while Shaws Bay East has slipped from Good last year to Poor.

Shaws Bay East Arm is rated Good, as is the Serpentine.

The results come as the red and yellow flags are raised for another surf lifesaving season across the Far North Coast this weekend.

Statewide, 79 per cent of the 245 monitored swimming sites achieved a Very Good or Good rating, with the NSW Government saying generally drier conditions had reduced stormwater runoff and pollution.

Ocean beaches performed particularly strongly, with 97 per cent rated Very Good or Good.

Estuaries, lakes and lagoons generally performed worse because lower water exchange can mean pollution takes longer to disperse after rain.

The Government recommends swimmers check current Beachwatch pollution advice, particularly following rainfall.

Meanwhile, Surf Life Saving Far North Coast will officially launch its new season with its annual Raising of the Flags ceremony at Brunswick Heads on Saturday.

Almost 1500 volunteer lifesavers across the Far North Coast performed more than 120 rescues and 9300 preventative actions last season, clocking up more than 47,000 patrol hours.

UPDATE: Ballina Shire Council has issued a Red Alert for Lake Ainsworth after testing detected high levels of potentially toxic blue-green algae.

Council is warning people not to swim, canoe or undertake other recreational activities involving contact with the lake until the alert is lifted.

Council says potentially toxic blue-green algae can cause gastroenteritis if consumed and skin and eye irritation through contact.

The Red Alert will remain in place until further monitoring shows the risk has sufficiently diminished.