Dolphins helped rescuers guide a stricken yacht to safety off Co Antrim, the RNLI said.
A Larne crew rescued two men on Wednesday afternoon after their vessel became tangled in fishing nets.
As it was towing them into harbour, some of the highly intelligent mammals, known in legend for rescuing humans at sea, swam alongside, captured in footage taken by the crew.
The boat had been travelling between Bangor and Campbeltown in Scotland when its propeller became tangled.
Weather conditions were good but there was not enough wind to sail in the absence of the engine.
A fisheries protection vessel assisted communications between the lifeboat and the yacht.
The lifeboat crew worked to establish a towline and proceeded to take the vessel under tow to Larne Lough, where it was met by Larne's inshore lifeboat which assisted in helping the yacht onto a mooring.
Dolphins that were in the area at the time also guided the vessel into the harbour, the RNLI said.
Roy McMullan, Larne RNLI deputy launching authority, reminded anyone taking to the sea this summer to respect the water.
"Sailing and motorboating are popular pastimes particularly at this time of year," he said.
"We would encourage sailors to always wear a lifejacket and always have a means for calling or signalling for help and ensure everyone onboard knows how to use it.
"Always check the weather forecast and tide times and make sure someone ashore knows where you are going and who to call if you don't return on time."