A coroner has warned theme park operators about the risk of future deaths unless they address safety concerns over water rides, after an inquest into the drowning of an 11-year-old girl.

The assistant coroner for south Staffordshire, Margaret Jones, has written a report for the prevention of future deaths to UK theme park managers, concluding an inquest into the death of Evha Jannath.

Evha was “propelled” from a vessel on the Splash Canyon river rapids ride at Drayton Manor in Staffordshire during an end-of-year school trip with friends from Jameah Girls academy in Leicester on 9 May 2017.

The inquest last month into her death heard how she had waded to the end of the ride after the fall but fell into deeper water while trying to climb an algae-covered “travelator”. She was later discovered face down in the water.

The inquest jury found that Evha died accidentally. In a statement released after the verdict, her family said they entrusted their daughter’s safety to the school on what should have been a “fun school trip”. They were “very upset” to learn none of the ride staff knew how to rescue Evha from the water and that there was no life-saving equipment available.

The coroner has sent the report to Drayton Manor, to Alton Towers, also in Staffordshire, Legoland in Berkshire, Thorpe Park in Surrey, Lightwater Valley in Ripon and the operators Merlin Entertainments.

Jones said the inquest evidence “revealed matters giving rise to concern”, adding: “In my opinion there is a risk that future deaths will occur unless action is taken.”

Identifying six matters of concern at Drayton Manor on the day of the incident, she said it was “not possible to adequately monitor CCTV” on the ride that day because staff had other tasks to complete. She also highlighted the fact that only half the ride’s route was covered by cameras.

Jones said there had been no safety warnings given to guests boarding the ride’s boats, and that warning signs were incomplete and in some cases illegible due to wear and tear.

The coroner added that no water rescue equipment was available to staff and they had not been trained in such rescues, and ride staff had “no clear understanding” of emergency procedures.

Concluding, she said: “Management staff did not accept that guest safety measures (CCTV, safety instructions and signage) had failed. In my opinion, action should be taken to prevent future deaths and I believe you have the power to take such action.”

The coroner also drew attention to a Health and Safety Executive (HSE) water ride safety notice issued to all theme parks immediately after Evha’s death, covering many of the issues raised at the inquest.

She asked for a detailed response to the report from Drayton Manor’s manager and replies regarding actions taken as a result of the HSE notice from all theme park managers nationally.

The coroner has given until 8 January for the parks to respond, although that period can be extended.

Copies of the report have been sent to Evha’s family and school, the chief coroner for England and Wales and Staffordshire’s Safeguarding Children board.

The ride, which has been closed since the incident, will not be reopened without approval by the HSE.