A man, a woman and a teenage girl from the same family drowned off Shoreham-by-Sea in West Sussex after getting into difficulty during a group swim, Sussex Police confirmed. A fourth family member, a younger girl, was pulled from the water alive but remained in critical condition in hospital.

The father was identified as Hossam Al-Khawas, a Palestinian refugee originally from Rashidieh Camp in Lebanon. The Palestinian Embassy in London confirmed his identity to the BBC but said it was unable to confirm the identities of the other family members who died.

Sussex Police said the family had been camping near the harbour and entered the water together for a swim. Chief Superintendent James Collis confirmed all four got into difficulty in the water and that next of kin had been informed.

Eyewitnesses said one of the children became caught in a fishing net, which is believed to have triggered the emergency. Local landscaper Joe Chrisp, 24, said he encountered a large police presence while returning from work. "It happened when I was on my way back from work. There were loads of police, and I got turned around. It's so tragic. One of the kids apparently got caught in a fishing net," Chrisp said.

Residents near the harbour say the area has a steep underwater shelf where the seabed drops away sharply and quickly, making it difficult for swimmers to keep their footing. The conditions in that stretch of water are not widely marked or signed for casual swimmers, according to local accounts.

The rescue operation drew an air ambulance, a lifeboat crew and specialist officers who searched the choppy water. Multiple agencies worked the site simultaneously.

Shoreham MP Tom Rutland said the family had been visiting the area. "My understanding is that they have been visiting the area," Rutland said. He added that it was too early to establish precisely where in the water the family ran into trouble and what sequence of events led to the deaths, but said the priority now was ensuring people swim safely along that stretch of coastline.

Jane Bartlett, associate vicar of the Church of the Good Shepherd, visited the site of the drownings and announced her vicarage would remain open throughout the day for community members wishing to pay their respects. "As a community and as a church, we're all holding everyone involved in this in our prayers — for souls of the departed, for the recovery of the girl in hospital, and for the strength, too, of the emergency services and the impact that it has on them," Bartlett said.

Rashidieh Camp, where Al-Khawas originated, is one of the established Palestinian refugee camps in southern Lebanon and has been home to Palestinian refugees and their descendants for decades.