Researchers near Seal Island off Mossel Bay came a bit too close for comfort to their subject when a great white shark landed inside their boat.

The 500-kilogram, three-metre long shark jumped out of the water and fell partly onto their boat on Monday morning, reported Beeld newspaper.

"That is not a situation I would want to go through again," said researcher Dorien Schroder.

The panic-stricken shark wiggled itself further onto the boat, damaging equipment in the process.

Schrober called for help and a second boat arrived and tried to pull the shark back into the ocean after tying a rope around its tail fin.

But the plan failed and the second boat eventually pulled the boat carrying the shark, who the researchers kept alive by pouring water over it, to the Mossel Bay harbour. There it was freed with a hook.

"The shark was panicky but no one's life was in danger," said Schroder.