Refugees and members of the public were invited to the beach party in Benone, Magilligan, on 3 September.
The North West Migrants Forum, which organised the event, became concerned after what they said were "strong opinions" posted on Facebook.
Police said they attended as part of their "keeping people safe" role.
"The event also provided the opportunity to engage with a cross section of the local community in a very positive way," police added.
The North West Migrants Forum offers support and advice to migrants in the Derry area.
It is understood that the group received some negative comments on its Facebook page after calling on people to "wear Burkinis to show support to our Muslim women".
"After very strong opinions expressed through our Facebook account and the ongoing Burkini debate, we were concerned that the event may be disrupted," one of the project co-ordinators told the Derry Journal.
"However we felt very relaxed and free to enjoy the barbecue and the beautiful beach experience without any interference."
A controversial ban on burkinis in the city of Nice in France was lifted last week.
Burkinis - full-body swimsuits - were not mentioned by name in the bans, with the order simply saying beachwear must be respectful of good public manners and the principle of secularism.
Organisers of the Benone beach trip said that it had been a well-attended and positive experience, and thanked police "for keeping us safe".
"We had two police officers who spent the whole day with us, they even let the children explore and play with their van," added the co-ordinator.
"The families were very grateful to have them there. They felt supported and that they belong.
"We hope that we will be able to organise another event next summer."
Some of the newly arrived Syrian refugees have been telling the BBC what life was like in their war-torn country.
A group of burkini-clad Syrian refugees were given a police escort to a County Londonderry beach barbecue after "concerning" Facebook posts.