The friends of a teenage boy who drowned in a lake on one of the hottest days of the year saw him 'gasping for air' but 'thought it was a prank', an inquest has heard.Declan Sawyer, 15, got into difficulty at Swanholme Lakes nature reserve in Hartsholme Park, Lincoln, on the afternoon of May 24.He had been out swimming with his friends but began struggling in the water while making his way to an island.An inquest in Grimsby was told Declan's friends first thought he was joking around - but that they tried to help him after realising he was in serious trouble, attempting to get him to float on his back.One friend said in a statement: 'I thought he was faking it but he didn't come up.'Another described seeing Declan 'gasping for air' but 'thought it was a prank at first'.And the fear of being pulled under water meant but they were unable to save him. The inquest heard a member of the public called emergency services at 2.20pm after hearing shouts asking for someone to call an ambulance. The family of 15-year-old Declan Sawyer, pictured, paid a heartfelt tribute to him after he died in a lake on one of the hottest days of the yearDeclan had gone to Swanholme Lakes - a nature reserve near his home in Lincoln - as the local temperature soared to 27C Swanholme Lakes is a local nature reserve and a nationally recognised Site of Special Scientific InterestDeclan's body was recovered from the lake at around 7pm following an extensive search.The coroner, who gave the cause of death as drowning, said: 'This tragic incident highlights the inherent dangers of swimming in open water.'Unlike controlled environments such as swimming pools, open water can present a range of hidden hazards, including cold water shock, strong currents, sudden changes in depth, poor visibility, and underwater obstacles.'Even on warm, sunny days, water temperatures can be deceptively low and can quickly lead to disorientation, breathing difficulties, and exhaustion.'These risks can affect swimmers of all ages and abilities, often with little warning.'The coroner advised anyone entering open water to assess the conditions, swim only where it is safe, avoid swimming alone and be aware of 'the potentially life-threatening consequences' of unexpected difficulties in the water.In a tribute to Declan read to the court, his father Carl described him as a popular boy, who loved football and fishing.'I can't put into words the effect this has had,' he said. Declan, pictured, was also said to be a keen fisherman who enjoyed playing football Friends added their own touching comments on social media in the hours after the tragic news'Declan was my boy. Our lives will never be the same again.'Mr Sawyer described the support the family had received as 'overwhelming' - adding it showed what a popular young man Declan wasDeclan's aunt Lindsey Sawyer previously released a moving Facebook slideshow marking cherished family memories of a life tragically cut short.The snapshots showed the youngster from a toddler as he grew up, enjoying outings to the beach, motorcycling and outdoor adventure sports.He was also said to be a keen fisherman who enjoyed playing football, and had met a group of his heroes from Lincoln City FC.Ms Sawyer posted: 'Words cannot describe how utterly heartbroken we are.. how life can change so fast and in such a tragic way… we loved you like you was our own , looking at all the amazing memories you shared with us….'RIP Declan forever in our hearts… x.'A huge search operation was mounted on May 24 at the former quarry using police divers and Declan's body was recovered in the evening.As police scoured the lake, the area was cordoned off from the hundreds of Bank Holiday visitors who had been enjoying the nature reserve.Swanholme Lakes is a local nature reserve and a nationally recognised Site of Special Scientific Interest.The day of the incident marked one of the UK's hottest May days on record as the local temperature in Lincoln soared to 27C.