A skipper was startled to spot a two-metre great white shark near his boat at a marina south of Adelaide on the Fleurieu Peninsula.

Jarrod Glaister, owner and skipper of the Southern Fishing Charters, was conducting maintenance on his boat at Marina St Vincent yesterday morning when he spotted something in the water.

“We thought it was a dolphin at first, but then realised it was a six, seven foot white,” he told 9news.com.au.

The shark came up along the side of the docked boat and the rocky edge of the marina.

Glaister, who has been running the company out of Wirrina Cove for four years, said he has never seen a shark come in as close to the marina before.

“We sharks all the time, but we’ve seen them out off the marina and in the open water. We’ve never seen any that close,” he said.

“That was definitely a sight, that’s for sure. We were obviously very surprised.”

Glaister said he noticed that the shark appeared sick.

“Because of the algae bloom, it obviously wasn’t getting enough oxygen, so he’s come in the marina there to try and find a pocket of oxygen, and I think he did too,” he said.

“We don’t reckon he would have survived at all. The damage had been done.

“He wasn’t healthy one bit.”

A microalgae bloom has been causing discoloured water and foam along parts of the Fleurieu Peninsula, Kangaroo Island and the southern coast of Yorke Peninsula since March.

It’s caused mass deaths of marine life, which have been washed ashore on coasts. 

The algae are not harmful to humans, but exposure can cause temporary skin and eye irritation and respiratory symptoms.

Experts believe the bloom is being caused by rising sea temperatures, which are 2.5 degrees warmer than usual, and calm conditions.

Government agencies are monitoring the situation, but advise that nothing can be done to dilute or dissipate the bloom naturally. 

The last time the state recorded a similar event of this magnitude was in Coffin Bay in 2014.