A German man, 60, was injured during what is known as a 'sofaboat ride' in St Paul's Bay, early on Saturday evening.
The police said on Sunday that his injuries were serious and Magistrate Natasha Galea Sciberras is holding an inquiry.
The police also reported that earlier on Saturday afternoon, a woman, 67, was injured when she fell down a shaft while working in her home in Sisters Street, Tarxien.
The police said she fell a height of one storey. She has been hospitalised.
Teenager hit by car
In a third accident, the police said that a 16-year-old Syrian boy was seriously injured when he was hit by a Mercedes car while crossing December 13 Road, Marsa.
The accident happened at 8.45pm on Saturday. The boy, who lives in Zabbar, was hospitalised.
The car was being driven by a 34-year-old man from Marsaxlokk.