18 August 2013
Last updated at 14:37
Spanish fishermen gathered for the protest off Gibraltar at the spot where 70 concrete blocks were dropped into the sea to create an artificial reef.
The reef has sparked heightened tensions between Gibraltar and Spain in recent weeks, as Spanish fishermen say it restricts their right to fish while the British territory says the waters belong to it and they should not be fishing there.
Chief Inspector Castle Yates, of the Royal Gibraltar Police, said "about 38 Spanish fishing boats and seven or eight pleasure craft" were involved in the protest. He said they crossed into Gibraltarian waters where police and the Royal Navy set up a cordon and "corralled" them.
Back on shore onlookers, including media crews and supporters of the Spanish fishermen, watched as those in protest boats tried unsuccessfully - according to Gibraltarian police - to breach the cordon.
The protest lasted for about an hour and saw a heavy police presence, including three large Royal Gibraltar Police boats and the same number of large Spanish Civil Guard boats, along with a number of smaller law enforcement speed boats.
Reuters news agency said this image showed a Spanish Civil Guard boat colliding with a Gibraltar police boat while the protest took place.
Leoncio Fernandez, head of fishermen from the nearby port of La Linea, held a red flare to mark the end of the demonstration. At its close, Gibraltar's chief minister Fabian Picardo sent a tweet praising Gibraltar and UK authorities for their "cool, professional and calm" approach to the morning's events.
Gibraltar has been under British rule since 1713 - but Spain disputes UK sovereignty over the rocky outcrop. In recent years the dispute has centred on fishing rights, with both sides claiming jurisdiction over the waters off the Rock.