A tourist has had a very lucky break, spotted drifting on a surfboard off the Australian coast nearly 6 kilometres offshore.

The 37-year-old Japanese man told police he got into trouble while surfing at Bulli Beach, near Wollongong, at about 5:00pm on Thursday.

A tourist was found floating on a surfboard by the crew of the MSC Damla. ( Supplied: MSC Damla )

He got into trouble in a current, tried to paddle back into shore, but the waves were too big, he told police.

"He was attempting to paddle back in for six hours before he ran out of energy and drifted at sea," Inspector Darren Wood from the Marine Area Command of NSW Police said.

"It went dark, and being by himself no-one knew he was out there."

He spent the night clinging to his surfboard and it is estimated he spent about 16 hours in the water.

Luckily, the eagle-eyed crew of the 300-metre long container ship MSC Damla spotted the man on top of his yellow surfboard.

As he drifted alongside the ship, the crew threw him a life buoy, and were able to pull him aboard.

He was given food and drink and warm clothing, and the crew contacted authorities. A boat was sent out to the container ship to retrieve him.

The crew of the MSC Damla were able to throw a life buoy to the man. ( Supplied: MSC Damla )

He was taken to Wollongong Hospital where a doctor said he was in surprisingly good health with high spirits, and he was discharged Friday afternoon.

Police said there was no active search conducted for the man, as he was not reported missing.

The surfer told the police he had travelled to Australia a couple of times before.

"He appears to be travelling by himself, and that was why no-one was alerted to the fact that he was stuck in this rip and that he was out there," Inspector Wood said.

"Lucky that he went past the vessel otherwise we wouldn't have known for some time that he was out there."

Inspector Wood also said the hot weather off the coast was a factor in the man's survival.

"He appeared to be in fairly good health considering he had been at sea all night, and luckily for him temperatures only dropped to around 21 degrees [Celsius] through the night which prevented him from getting hypothermia."

The Port Kembla Water Police intend to return the surfboard to him on Saturday.

"This incident is a reminder of the need to let people know your plans before setting out, as well as the importance of knowing local conditions," a spokesperson from Surf Life Saving NSW said.