An 18-year-old man has been taken to hospital with injuries after a possible assault at the Trecco Bay caravan park in Porthcawl.
The incident was reported at around 8am on Sunday morning.
South Wales Police is asking anyone who may have seen anything suspicious in the area overnight to contact them.
Organisers say a record 1,500 swimmers took a dip in the sea as part of Porthcawl's Christmas Morning Swim.
A further 3,000 spectators are estimated to have watched on.
The event is marking its 50th anniversary, and raises money for a number of local charities and organisations.
Huge crowds have turned out for the Porthcawl Christmas Morning Swim.
The event is celebrating its 50th anniversary, and raising money for local charities and projects.
More than 1,000 people are expected to brave the cold sea later, as Porthcawl Christmas Morning Swim marks its 50th anniversary.
Organisers are hoping for a record attendance, at what is now one of the UK's largest festive swims.
Swimmers are due to gather from 10.30am - before the official start at the top of the beach at 11.45am.
The event is raising money for a series of charities and local projects.
Jennie Griffiths from South Wales Fire and Rescue Service says that the large fire in Porthcawl involved around two acres of thick gorse which is well alight - and firefighting efforts are likely to continue for 24 hours.
Update porthcawl: fire involving 2acres of thick gorse well alight. Incident is deep seated + likely to be protracted for 24hrs
Update Porthcawl: Crews have also requested a JCB as this is a deep seated fire which will require digging out
Update Porthcawl: Crews have requested a welfare unit at scene they have been firefighting for 3hrs + require supply of drinking water
South Wales Fire and Rescue Service says around 25 firefighters are now tackling a large blaze on the seafront in Porthcawl.
A fire service spokesperson confirmed they are trying to bring the fire under control quickly, due to concerns it may spread, in a strong breeze.
South Wales Fire and Rescue Service said around 70 square metres of grass was "well alight" on the seafront in Porthcawl.
Approx 70sqm of grass well alight at The Esplanade/West Drive area in Porthcawl. 5 appliances and a wildfire officer in att. #SWControl KA
South Wales Police is advising drivers to stay away from the Locks Common area, with road closures due to the blaze.
There is a large grass fire on the seafront in Porthcawl.
Five fire appliances are fighting the blaze, which has caused road closures in the West Drive and Locks Common area.
More than a thousand people took to the beach in Porthcawl earlier to raise money for charity.
It involved running five kilometres and getting covered in paint.