Labour Party ads on Facebook today state that water company bosses face two years in jail for polluting rivers.

That's a lie. A new law comes into force today which 'could see water bosses who cover up illegal sewage spills' jailed.

That's a very, very different thing.
https://www.gov.uk/government/news/polluting-water-bosses-face-up-to-two-years-in-prison