The first day, of what is expected to be an eight-day hearing, at Peterborough Town Hall, was told Rebecca Louise Hellens, of Chatteris, died at Bedford Hospital shortly before 1pm on July 26, 2015, after the incident at the South Lakes Ski School, in Little Paxton, near St Neots. Miss Hellens, who was described as an experienced and competent jet skier, was involved in a collision with another jet ski which was being ridden by her friend Nicholas Rudd who was said to be less experienced. Paul Hammersley, who ran the ski school until December 2016, told the inquest he was a qualified water ski instructor but was not qualified to teach anyone how to jet ski. He explained that those wishing to jet ski provided their own equipment and although they were asked to sign in and provide details for insurance purposes, he had no involvement with the jet skiers and the activity was self policing. He said there were rules, but admitted they were not displayed at the clubhouse, but said anyone wishing to participate was handed a copy of the rules and asked to wear a lifejacket or buoyancy aid. He told the inquest that beginners were asked to use the middle section of the lake and all jet skiers were asked to ride in an anti-clockwise direction at all times. When asked by assistant coroner Simon Milburn how the jet ski operation was regulated he confirmed that other club members would inform him of any breaches of the rules. I dont sit there all day long, he said. People have done things that are just plain stupid and they have been asked to leave, he explained. When asked how the rules were put together, he replied: By trial and error. Mr Hammersley told the inquest it was raining heavily on the day Miss Hellens died, but there was no policy for refusing to allow people to jet ski due to bad weather, although he had cancelled all but one of his water ski lessons that day. It was while he was on another part of the lake carrying out a water ski lesson that he noticed a commotion. He arrived at the bank and saw someone performing CPR on Miss Hellens. He said he spoke to Mr Rudd who was shaken up and told him I hit her. We all thought she had drowned as there were no marks on her at all, said Mr Hammersley. The inquest was told that after the collision; Miss Hellens was pulled unconscious from the water. She went into cardiac arrest and despite attempts to save her she died later in hospital. A post mortem examination showed a tear in her aorta and massive blood loss to her chest cavity.The inquest continues.