Surfers on the South West's packed beaches are reporting a number of incidents of so-called surf rage.
Surfers dropping in on each other's waves cause ripples
They claim tempers become frayed because the sea is so congested as a result of the rapid growth in the sport.
The British Surfing Association says at the moment such incidents are rare.
But it is encouraging would-be surfers to have lessons with approved instructors to learn how to avoid trouble.
More than 2,000 surfers, body boarders and swimmers can pack the sea at Fistral Beach near Newquay at its busiest.
Lifeguard Tristan Perry says that it can lead to surf rage.
He said: "It is just a case of too many people and too few waves so the local people get a bit annoyed when they see people they have not seen before crowding it up.
"It is like road rage, but in the surf."
The most regular cause of trouble is so-called dropping in, when a surfer on their board is confronted by someone else joining the wave.
Toby Shoebridge from Sussex, said: "Someone had a bit of a shout at me when I got on his wave.
"But when you're waiting 10 minutes for a wave it can be a bit of a pain when you have to get off it."
The British Surfing Association says incidents are rare.
But its national director, Dave Reed, says surfers do get upset.
He said: "Sometimes people's tempers do get a bit frayed when they collide and some people are a bit ignorant of surfing conditions and other people in the water."