The incidents occurred at Ballynamona Beach with coastal cleanup group, Clean Coasts Ballynamona, working hard to restore the beach after it was left wrecked.
On Sunday morning, the first beach clean up the group has held since the lockdown, volunteers arrived on site to find Ballynamona Beach in a complete state.
Campers had left broken glass bottles and other rubbish on the beach.
They had also burnt some of their camping gear.
"We regret to inform you that all users of Ballynamona Beach need to take extra special care due to the moronic behaviour of a small few," the Clean Coasts Ballynamona group wrote on social media.
"At our first beach clean this morning since the lockdown, we were greeted by the remnants of two campsites where irresponsible people had left tents, chairs, and pretty much everything after them.
"Not only this, but they smashed a lot of the glass bottles leaving the ground really dangerous for everyone.
"We picked up what we could see, but there is the strong possibility that there is more sharp broken glass there that we didn't get.
"Please be vigilant, especially with small young children," they warned.
"Ballycotton Bay (Ardnahinch, Ballynamona and Silverstrand) is a Special Protection Area and it is illegal to camp, light fires use vehicles in, on or around the beach," the group stated.
A second incident of wanton littering occurred last night.
Clean Coasts Ballynamona thanked Gardaí for responding to a disturbance at Ballynamona Beach.
In a statement Gardaí said:
"Gardaí from Midleton attended Ballynmona Beach after a large group of youths had gathered in the area.
"Gardaí spoke to the group and advised them of Government regulations surrounding groups gathering.
"The group complied with Gardaí and left the area.
"Midleton Gardaí will continue to monitor Ballynamona beach and surrounding area."