Four NSW beaches will have free wi-fi this summer under a state government trial to alert sunseekers to potential hazards, including sharks and dangerous surf conditions.

The technology, which will be announced today, will initially be used at Byron Bay, Bronte, North Cronulla and North Wollongong and follows similar trials underway on Queensland beaches.

The alerts will be pre-translated into five languages other than English including Chinese, Arabic and Hindi.

The wi-fi signal will be targeted within an area of around 100m to encourage people to stay between the red and yellow flags.

Police and Emergency Services Minister David Elliott said the program would give surf lifesavers the tools they needed to save more lives.

"We're committed to reducing these tragic and too often preventable drownings and that's why we've invested $16 million in Surf Life Saving NSW over four years to enhance their rescue capacity and better educate the community on water safety," he said.

Surf Life Saving NSW chief executive officer Steve Pearce said he was pleased the trials are being rolled out right along the coast.

"With two tragic coastal drownings in the last few days outside patrol areas, the hope is that this technology will encourage more people to swim between the flags," he said.

"For us, the benefits are twofold; it's a great way to encourage swimmers to stay between the flags, but it's also a platform to provide live information on conditions and safety tips, particularly to international tourists in their own language."

The trial starts Saturday.