Spectacular footage captured over the May Bank Holiday weekend in West Clare, shows what the swimmers described as '20-30' basking sharks.
Former lifeguard Tom Gillespie had surfed his whole life and has seen all sorts of ocean life, but had never seen as many basking sharks together at once.
"You could see that the sea was rich in plankton, possibly due to the winds blowing offshore for so long." Tom told Independent.ie.
Tom and his friends, who were also experienced surfers, made sure to act calmly and avoided touching the creatures.
"We know the sea and that coastline very well and know when the conditions are safe to go out. We were also very respectful of the creatures and we were sure to be as calm as possible when the swam past us, and we never attempted to touch them.
"It was an absolutely awesome experience that we will never forget and I feel very privileged to be living in the area at the moment. "