Prince's Sporting Club in Surrey has pleaded guilty at Southwark Crown Court to corporate manslaughter after 11-year-old Mari-Simon Cronje died when she was hit by a boat towing the inflatable she was riding.
Company director Frederick Glen Walker was cleared of any offences after the Crown Prosecution Service dropped charges against him.
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Police have released an e-fit of a man suspected of attacking her.
The force has been tweeting after carrying out a series of dawn raids.
Adenike Akingbogun made the dangerous manoeuvre after ignoring the crossing lights and driving onto the tracks.