Amorous basking sharks are being blamed for a spate of sightings of potentially dangerous mako sharks off Cornwall.
A second suspected mako - Maori for man-eater - was seen off Bude in the north of the county on Tuesday night.
A fisherman said he saw a 12 to 15ft-long mako, one of the fastest fish in the sea, leap out of the water.
But a shark expert told BBC News that he suspected harmless male basking sharks, seen nearby in the morning, were showing off to female mates.
Douglas Herdson, of the National Marine Aquarium in Plymouth, said: "I have reports from St Isaac, 20 miles south of Bude, of a group of basking sharks and three of them jumped from the water.
"Sometimes a female will be followed by a large group of males and we suspect jumping could be courtship behaviour.
"If that was happening in the morning at St Isaac, the chances of it happening off Bude in the evening are pretty high."
He added: "Makos are pretty big, but 15ft would be big for a mako and normal size for a basking shark.
"My feeling is that it is a case of mistaken identity."
Makos have long been summer visitors to the region, chasing shoals of mackerel.
'Nothing to be afraid of'
The record for the biggest fish ever caught off the UK was a mako, hooked off Plymouth in 1971 and there were confirmed sightings going back to the 1950s.
But makos were still a rare find and if they did visit the area, they would normally remain off-shore, hunting for food.
Mr Herdson is convinced that a previous sighting of a mako, which led to surfers being called out of the water at Gwithian on 20 July, was not a mako, but a basking shark.
"There is nothing to be afraid of. Out of all the thousands of shark attacks in the world, only eight have ever been reported as a mako," he said.
"What we have to remember is that these sharks are highly specialised fish-eaters, not man-eaters. There has never been an unprovoked shark attack in UK waters."