A search has been launched for a man who disappeared while swimming at a beach in Sydney’s south.

A man thought to be in his 30s was seen in difficulty about 100 metres offshore at 11am today at Little Bay Beach near Maroubra.

Officers from Eastern Beaches Police Area Command, along with Marine Area Command, PolAir, Marine Rescue NSW, Surf Life Saving NSW and the Westpac Rescue Helicopter, started searching.

A man thought to be in his 30s was seen in difficulty at 11am at Little Bay near Maroubra, about 100m offshore.© Supplied

Marine Rescue NSW Inspector Joel Pemberton said the organisation’s rescue vessels Botany Hacking 30 and Middle Harbour 30 were deployed.

“Both Marine Rescue NSW vessels are working alongside water police, searching an area from Little Bay Beach to Cape Banks in the south,” he said.

“Sea conditions offshore are unfavourable, with a three- to five- metre south-east rolling swell.”