The 30-year-old Thomastown man got into trouble around 2pm about three kilometres off Lawrence Rocks in Bass Strait.

He activated an emergency beacon, triggering a response from water police, airwing and coast guard volunteers.

But Portland police Sergeant Ash Rawlings said local anglers from Reel Time Charter Fishing came to the rescue before the services could reach the stranded man.

"Due to the large number of tuna fisherman down here, they are all very well equipped and look out for each other," he said.

"The male was very lucky."

The charter boat towed the jet ski safely to shore, and Sergeant Rawlings said the cause of the mishap was not yet known.

"We are unsure whether it's vessel issues or whether he was swamped by a large swell. Investigations are early on," he said.

"We just want to reiterate the importance of having the correct safety gear and knowledge of where you are fishing or boating."

An Ambulance Victoria spokeswoman said one person was taken to Portland Hospital in a stable condition following the incident.

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